Yeah, the social media world has gone through at least three generations of complete overhaul since this forum was started. Back in Net pre-history (or at least well before this forum started) there was USEnet. Then came web BBS/forum systems like this. Then came social websites like LiveJournal and MySpace. Then came FaceBook, and after it G+, Twitter, Tumblr and Instagram, and off to the side came WhatsApp, Telegram, SnapChat, Discord, and who knows what else. It's impossible to cover them all, and many of them simply don't provide the kind of focussed communication a web forum can. Even there, within our relatively specialised technical niche, there are more generally accessible places (like Cloudy Nights) for wide-spread discussion with like-minded folk. You can't cover them all, but plenty of folk will try to cover at least a few, and the more you try to keep track of the less time you have for any particular one. When there's one place everybody's there. When there are dozens (or hundreds, or thousands) the folk are far more scattered...
As for the signing-up process being complicated; well, we just ask folk to request access, and then we add them to the system manually. We turned off the normal registration process years ago because we got many many sign-ups that way, but only a very small fraction of them were genuine.