people struggle with the concept of federation and picking a server

This is a HUGE reason. I didn't know when I first signed up for Lemmy that I was on what is essentially a tankie instance. I didn't know when I signed up for Pixelfed that I wasn't going to be able to see shit because the first server I signed up for wasn't really federated with anyone and I've mostly given up on it. I still can't see a bunch of stuff on Mastodon without switching through several accounts with no rhyme or reason.

I've said before that I obviously like it here because I'm using the services, but it's not easy. Most people don't know about the fediverse, and most of those that do want to be passive about maintaining their social media. Most of the fediverse is built for nerds.