It has a lot to do with federation issues on the modern internet.
- Version mismatching and updates
- Running the servers (admin, setup, config)
- Spam and problematic users
Urbit ID fixes the spam issue, Urbit OS fixes the admin and version update issues. Mastodon (but really any non-urbit system) is going to always be a mess of dependencies and things that break.
This old post (2010 before urbit was a real thing) goes into most of it: http://moronlab.blogspot.com/2010/01/urbit-functional-progra...