Thinking that a community lives in a git provider is a bad idea. It shouldn't matter who hosts a git instance, and I would argue it's better to fight for diversity here.
It might be better to fight for diversity, but I was pointing out the actuality of it all. Networks effects are real, and this isn't the project I want to see die because of it.
So, github is the daily workflow for many people. You're in it, your around it, your using it. It's kind of the same as out-of-sight, out-of-mind.
If I want to, I can signup for yet another site and do git-things with this codebase, but I have to change my daily process to include a one-off change to a new location. There are real costs with this mental flow change.