Reddit still works as a platform because it's where all the users are. It's no different to the rest in that regard. They're not "prisoners", nor are they idiots for staying if the current platform works for them. Joining Lemmy/the Fediverse is a choice, and if they choose to join they should be welcomed.
Maybe, but it’s probably more about apathy and being unaware about alternatives.
My wife very rarely goes on Reddit. She doesn’t even have an account. The only reason she knows about the fediverse is because her nerdy husband won’t stop talking about it.
Reddit still has a lot of content on here yet. A lot of communities are not active, too small or non-existent. Tech communities are thriving here, but that's really it. Many people won't stay until some of those communities fill out.
I was permanently banned because I was banned from a subreddit and made another account years later and was accused of skirting a ban. Was it justified? Maybe. Was it good for me? Yes. It freed me from the shackles.