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.
“Celebrities” is quite a broad term.
I guess most people here were thinking about people they don’t really share values with (let’s say reality tv influencers for instance). On the other hand, if someone like Keanu Reeves for instance would do an AMA here, I’m pretty sure everyone would be happy and thankful for them to put some light on the Fediverse