Yeah, I cannot recollect getting a useful answer there. Google rarely links to it; the links are often questions without answers (I searched for my question terms after all, not knowing the answer).
And why delete anything? Surely they are not running out of space. I'll volunteer $100 so they can buy another Terabyte to store those deleted discussions.
My pet theory is that it's something I've come to think of as the "WELL effect". Named for the famous online community which I was a member of for approximately one month in the early 2000s, and which is still talking itself up for how vibrant it was 20 years ago but hasn't been vibrant for any time during this century.
It works like this: The oldsters perceive that they enjoy a certain elite status by virtue of how long they've been there, and begin to think of themselves as the "keepers" of the community. They also develop a measure of contempt for newbies, perhaps because they (being new) want to talk about things that the oldsters have had a chance to discuss many times before. And perhaps because they (being new) represent a slightly different culture, which triggers stereotypical "kids these days" instincts.
So they begin taking measures to protect the site from junior members. A positive spin is put on it by calling it "upholding community standards", but it would be just as fair to negatively characterize it as "telling those damn kids to get off my lawn." I suppose which one you think it is depends on whether you're the one yelling or being yelled at.
Either way, the terminal point is that everyone has gone to have fun somewhere else, essentially because that's precisely what they had been told to do, and all that's left is a hoary old collection of ossified cucumbers fondly remembering how much fun they used to have and wondering where the magic went.
When I joined WELL they had introduced forums that were only intended for people who joined during a specific calendar year. Presumably it was an attempt to try and counteract the effect somewhat. Personally, it just made me feel ghettoized.
At an old-fashioned web forum I used to run we toyed with the idea of closing down and archiving old threads after they reached a certain age. The idea was to try and codify our opinion that old conversations might be worth preserving for posterity, but they aren't a substitute for new conversations and shouldn't be used as an excuse to stifle them. Never actually got around to implementing it, though.
And why delete anything? Surely they are not running out of space. I'll volunteer $100 so they can buy another Terabyte to store those deleted discussions.