It’s exactly like email. You can have an email server @yourdomain that just has the one account, and interact with the rest of the email “network” just fine, right? Same with Mastodon.
People discovery isn't necessary with email, but it is for a social networking system.
I want to be able to find other people in the fediverse, and I also want people to find me. Having your own server excludes you from other people's local timelines (and vice versa), making discovery in both directions very challenging.
