Why have most of the older posters I recognise retreated here to meta
Older posters? I think they've been the ones who've been posting the most in Meta for a long time now. It's the newbies who've started posting here recently, and they're the ones who are doing so, probably to earn merit.
As for myself, I've always been interested in the drama and politics of bitcointalk (and of bitcoin in general), which is why I joined bitcointalk in the first place--in addition to the fact that there's very little censorship here in terms of language and ideas. Many other forums have rules about what you can talk about and how you can express yourself, but bitcointalk is relatively free. I'm aware of the profanity rule, but it doesn't get enforced (and should get repealed IMO).
Sometimes I post in IT or SD, but a lot of those threads don't interest me, or like suchmoon:
I feel I'm much better off just quietly reading it rather than publicly showing off my stupidity by trying to comment on it.
As I've said many times before, there are some brilliant people on bitcointalk who understand crypto, math, and other tech subjects at a level that I'm in awe of. My contribution would be on the level of a bounty shitposter if I tried to comment in some of those threads. I do have some economics education, and it's enough for me to make informed comments on some threads, but the Economics section is where I see most of the topics I'm interested in.
Plus, IT and SD are like P&S and Off-Topic for senior members, and I'm not into politics or discussing in
most of that sort of stuff.