I want to run, and enjoy running, Mastodon because it's the most Twitter like experience and for 14 years that's where I spent a lot of time.
I've never been a huge consumer of other social media platforms, so I don't feel equipped to run their open equivalents.
It's why I don't run PeerTube, Pixelfed, Calckey, or any number of really cool alternatives. I run Matrix as a "Fling” for our Mastodon users, but it's sort of it's own little world.