Reason mentioned in their About page. Inter-instance wars and the upkeep of a Mastodon server is not a joke.
May 10th, 2023: Update Folks, I’m thinking about closing down home.social later this year. Moderation efforts and “inter-instance-wars” have become a nightmare and I consider those a fundamental flaw in Mastodons core design. I also have come to believe, that larger instances might defy the purpose of the fediverse. You might want to start migrating accounts to other instances.
You might also want to read this thread.
No way to monetize. If you try and charge a subscription or gasp run ads on your instance for your users’ eyes only, you get de-fedded.
Mastodon’s scaling is appalling
Being a mod on any platform is miserable because there are a lot of bad actors
The only ones that have managed to properly square the circle are the big ones like mastodon.social that are funded by massive Patreons
Super instances thing is also super likely. We saw the same thing happen with email
Constant fear of being de-fedded less you piss off some admin or an influential user of some big instance