Only saw one or two people state they were leaving, but got a bunch of people I follow who no longer post and I'm guessing it comes down to:

* the lack if market capture. It's small here, you probably can't follow most people you might seek out if you're not already interested in the ecosystem.

* no algorithms. Great if you have a bunch of people you follow and want to see their content, but difficult to build that up in the beginning.

* technical complexity. Random tech nerds like us might enjoy it, but if tech isn't your job/hobby it probably feels needlessly complicated.

The one guy I remember explicitly saying he was leaving (who's name I can't remember) just wasn't interested in constant tech talk.