Because let’s say you’re Tom Hanks. And you get TomHanks@Lemmy.World
Well, what’s stopping someone else from adopting TomHanks@Lemm.ee?
And some platforms minimize the text size of platform, or hide it entirely. So you just might see TomHanks, and think it’s him. But it’s actually a 7 year old Chinese boy with a broken leg in Arizona.
Because anyone can grab the same name, on a different platform.
Use a better client that shows you the information? The default UI does, so that’s firmly a problem you’ve inflicted on yourself.
I’m just using a web browser that came with my phone. And if they were all hidden, it wouldn’t matter.
You’d just register your username. And this would be good for all the fediverse platforms. Once you register your innitial name, only you could register other services under that name. So it’s always you. Even if you never register for a service, you registered the name.
Then, if you register a new service, even years later, you still have your name.