I think it’s the same reason YouTube can keep shooting itself in the foot and still thrive: it’s where all the eyeballs are concentrated now.
Yeah…it is difficult to jump ships and try out another service - even when the other service is generally a better option than the previous one - if you don’t get an audience big enough to even bother starting with the otherwise better service.
I think I’m gonna disagree with the fandom dying thing.
From a system’s perspective - if it exist for a reason, for someone to use it, and then they stop using it and go away, leaving it alone without any use, I’d see that system being abandoned, lost, or dead.
Then again - someone can come back to it and turn it “alive” or active again!