Also, the inability to move existing posts or DMs from one instance to another discourages Twitter blue-check types. What if your instance is blocked by others? What if your instance shuts down?[1] What if you change jobs? (I think the last is why we haven't seen CNN or BBC or Yale create an instance and its people start using it.)

[1] Such as the recent spectacular implosion of mastodon.lol after its owner got horribly abused by members over Hogwarts Legacy. <https://news.ycombinator.com/item?id=34748195>