Some people talk of it as if it's a matter of principles. That even remaining as a free user in an unprofitable platform is making it pay off, like Elon Musk wins as long as people stay there, as if it was solely about Elon's pride and not the millions of people who still use it for community or professionally.
Seems like a variant of that generalized disdain that a lot of people have for social media they don't use.
It's one thing to promote the Fediverse, it's another to say that whoever doesn't immediately move over is to blame for everything bad being inflicted on them, which is reductive to say the least.