From what I understand Eve takes a lot of real-time investment and dedication to succeed.
After you get far you have to maintain the relationships you built with people, and the responsibilities you share with them.
Tribal Wars (unfortunately now pay to win) and Puzzle Pirates are two games I've played that share that aspect, though both have no where near the same amount of mechanics, content, and dedicated playerbase.
But yes, if lack of enjoyment/reward crosses a threshold, players quit. Which often forfeit their position in these kinds of games.
edit: Not sure on the "rejoinability" of Eve, I assume it relies on the player's progress and social standing, multiplied by how lax the in-game trading rules are. (Giving away ships+currency before you quit, getting ships back when you rejoin)
Often people who are leaving will either have their assets moved somewhere they'll certainly have access to later or just liquidate (generally on better than firesale terms).
Citadels (like the keepstar that changed hands) work differently: you can get everything in a citadel moved to the nearest suitable npc station at the cost of 15% of its value and a 20-day wait, worst case (google "eve asset safety" for the full details).
I owe my closest friendships and even my career to EVE. I'll expand on this in a bit.
While I did spend a few years floundering around in the game like most players do, I was lucky enough to get close to the major political action early on when the first alliance I was a part of, ISS, collapsed. The ties and relationships that I built here got me in-system to watch the first (BoB) Titan kill with my own eyes.
A few years later when wormhole space opened up, I jumped on that immediately and got involved with a corporation dedicated to taking advantage of the new resources and PvP opportunities. Within a few months I was an officer in the corporation and we had brought in some local blues doing manufacturing in a merger. I had a pretty good relationship with these guys; a group of three students from Denmark.
It became clear to me right away that my corp's CEO plan here was to screw these guys over and steal all of their assets, as well as the rest of the assets of the corp and do a runner. Without cluing him in, I managed to help everyone in my corporation secure their assets and he got away with nothing but the corp's wallet, which I made an effort to drain (spread out to members) and left only about 8bil ISK.
Immediately after, these students and I joined one of the most well known RP/lowsec PvP corps in the history of EVE and started our own manufacturing corporation on the side which turned into somewhat of a mini-empire. The students were programmers and I now had a practical use for a life-long hobby(but not really the inclination or skills to do professionally at the time).
One of them is probably my closest friend today. We routinely discuss the idea of one of us relocating and starting a real business together.
Other friends that I made in this corporation I still talk to on a daily basis...even after a few years away from EVE. Eventually our CEO had to shutter the corporation, as he took a job with CCP; most of us were getting older and finding it hard to find time for the game anyway and quit, myself included.
My account still has a few hundred billion ISK sitting in its wallet. I resist the urge to pop in and get deep into the game again, but it's frequently there. I've had some breathtakingly beautiful moments and experiences with people in my life because of this crazy game.
I'd done just about everything you could do in the game while I was playing it and had about 4 accounts at any given time. A lot of quitting players complain about not being able to find the real action in the game...while it's hard, everyone who can read the forums can find out who the important, active corporations are in game. Seek them out, be available and make friends and then make enemies.
For those not aware, Vile Rat, AKA Sean Smith , was one of the 4 Americans killed by terrorists in Benghazi, Libya on 09/11/2012.
This is an excerpt from a Kotaku piece on him (which has some good stories about his EVE exploits as well as real life stories ):
For the State Department, he was an Information Management Officer. He was an expert IT guy who signed up for postings in places both safe and dangerous. He was in Pretoria and Baghdad, Montreal and The Hague and then—for what was only supposed to be a few weeks—Benghazi, Libya. It is in that last place where he and three other Americans, including the U.S. ambassador to that country, were killed on September 11, 2012, by anti-American militants. It's there that his story was cut too short.
In Eve, Sean briefly was in the top echelon of the game's player-run government. His influence in the game actually grew for more than half a decade. He rose from ordinary player to master spy to diplomat for the mighty GoonSwarm alliance. He toppled rivals with the soft nudge of verbal persuasion. He helped his alliance win a war among player alliances that raged for three years. He even made peace with the Russians.
Again, there's a lot more about him in that Kotaku piece . This  piece in Forbes might be worth a look too, to see his diplomatic skills being put to use on reddit (EVE-related).
An excerpt -- I added a few paragraph-breaks:
If you play this stupid game, you may not realize it, but you play in a galaxy created in large part by Vile Rat’s talent as a diplomat. No one focused as relentlessly on using diplomacy as a strategic tool as VR. Mercenary Coalition flipped sides in the Great War in large part because of Vile Rat’s influence, and if that hadn’t happened GSF probably would have never taken out BoB.
Jabberlon5? VR made it. You may not even know what Jabberlon5 is, but it’s the smoke-filled jabber room where every nullsec personage of note hangs out and makes deals.
Goonswarm has succeeded over the years in large part because of VR’s emphasis on diplomacy, to the point of creating an entire section with a staff of 10+ called Corps Diplomatique, something no other alliance has. He had the vision and the understanding to see three steps ahead of everyone else – in the game, on the CSM, and when giving real-world advice.
Vile Rat was a spy for the Goonfleet Intelligence Agency. He infiltrated Lotka Volterra; he and I cooked up a scheme where we faked VR blowing up one of Sorenson’s haulers full of zydrine in Syndicate – this was back in 06 when zydrine mattered – and that proved to Lotka Volterra that he had gone ‘fuck goons’. BoB invaded Syndicate, then shortly thereafter GSF went to Insmother, allied with Red Alliance, and plowed over Lotka Volterra’s territory, all with Vile Rat’s aid. He came back in from the cold and became one of the most key players in the GSF directorate.
His influence over the grand game and the affairs of Nullsec cannot be overstated. If you were an alliance leader of any consequence, you spoke to Vile Rat. You knew him. You may have been a friend or an enemy or a pawn in a greater game, but he touched every aspect of EVE in ways that 99% of the population will never understand.
BTW, this isn't just some random podcast -- TLDR was a podcast put out by "On the Media" , the (US) public radio show that dissects how news is presented to the public, how the media works, etc. This episode was released in Jan. 2014.
A month later, a version of this TLDR episode was broadcast on the actual "On The Media" radio show  -- basically it's the podcast-episode with some added introductory material about the Benghazi story, narrated by Bob Garfield, one of the show's hosts.
(BTW, if you listened to the podcast link from emerongi above, there's no real reason to listen to the "On the Media" link below , but as someone familiar with the radio show, I found it interesting to see how it was presented on the actual show).
Ultimately you can spend a whole night trying to find fights in Eve and get 2 or 3 fights that last 20 seconds.
Or you can play 10 matches of overwatch or CS:Go or DOTA that last 30 minutes in the same time.
It still doesn't have a decent competitor though, elite dangerous is rubbish, still waiting on Star Citizen.
Longinius Spear once quoted Ernest Hemmingway, in a presentation at Eve: Vegas, "There is no hunting like the hunting of man, and those who have hunted armed men long enough and liked it, never care for anything else thereafter."
Personally I think that if you believe that you're still in the delusion phase where you're projecting your fantasy of what playing Eve should be like, compared to what playing Eve is actually like. That fantasy lasted a long time for me, like 3/4 years.
In reality battles are copying someone's prescribed fit, click a direction to align, letting your squad leader warp you. Eventually you might actually get a fight, which consists entirely of clicking the first name on an alphabetically sorted list and pressing F1. There's no skill, only the adrenaline rush of losing something you spent 2 weeks grinding for.
And don't forget, you spend 2 hours or even days between each of these battles waiting to even start the fight.
The big contradiction in Eve is that the thrill comes from permadeath, but it's only a thrill because the grinding is onerous. If everyone had infinite isk, no-one would play it because the fundamental combat gameplay is super boring.
Edit: Actually I prefer this response:
I think how true an EVE player finds the above statement is a good indicator of how effectively they played the game to begin with.
If you want the kind of rigid corp structure EVE offers but in a high-action game, I'd say look at some of the dedicated ArmA groups; particularly ShackTac.
The combat side of EVE is best played as more of a situation room. Sit and monitor comms and see what's going on over a wide area of space (read a book or do something engaging while you do this), then plan a surgical strike, execute and get out.
EVE is a role playing game - you play the role _you_ want to play! You live a life in EVE, as though you might live a life in the real world. You choose to trust people and make friends, may be get betrayed, or do the betraying yourself.
You fight an enemy because he/she is trying to steal your stuff, or take over an area that you want to keep owning.
Even though eSports games have more action, it's not the same kind of thing, and there's less thrill because losses in eSports are temporary. There's always a next game. Losses in EVE feels real, because they _are_ real!