Why do things go viral? I don't know, it appears to be somewhat random or luck based though. Why one cat's face can become a "hit" and apparently make its owner almost $100m versus the "funny" faces of many other cats certainly eludes me.
Why one good looking guy at a marathon can be catapulted overnight to widespread recognition over other equally good looking people at marathons also eludes me.
Should we care? Well, it's clear there's money to be made off it, and quite a lot of money at that, so the phenomenon certainly warrants at least some attention.
If it's seemingly so easy to catapult something to recognition and "fame" then figuring out what's behind it could also very easily be used for propaganda. If people are working on it for that reason then we certainly should care.
But this is a poor distinction. All memes as we think of them are artificial. There's nothing more natural about the changing shape of pottery than there is about cropping a photo and applying text to it.
A meme is a idea, an element of culture. When they spread they persist. The idea of making an image macro is a meme, the idea to share it online is too, the subject is too. They are more or less effective depending on how likely they will be shared. If I were to make an image macro that wasn't interesting and nobody else repeated it, it's still a meme, but it's impotent and it dies out.
The difference between image macros and pottery is more to do with how we communicate and how we handle new ideas. The Internet makes exposure to these things so much wider. But similarly we pass them on because of the simple feedback that we get, the e-pats on the back, the LOLs, the well playeds, the trolling. This is also promoted by the wide exposure. If you post an impressive image macro to the internet, you might get a response from 1% of the people who see it. You might get someone to copy it 0.1% of the time. In a place like reddit that might mean you have it copied 10 times for one post. If you were in ancient Assyria and you developed some equally impressive pottery technique, you'd be lucky if one person you show it to appreciates it and incredibly lucky for someone to want to copy it.
The Internet is kind of like a rainforest or coral reef for memes. Food is abundant, so all sorts of small but curious diversity pops up. They're not the most effective ideas, just the flashiest, and in some ways this might detract from the strongest ideas because they're not as flashy.
But that has nothing to do with how we define memes, but rather how easy it is to share information on the Internet. I don't think you can say it's a good thing or a bad thing. There's a lot of diversity in ideas with something as abundant in meme food as the Internet, it leads to a bit more chaos and people, genetically, are adapted to a much slower rate of information and change.