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.
@Lost_My_Mind let’s be honest, 99% of celebrities will use threads unless there’s a more popular and better designed activitypub alternative (spoiler: it wont happen for YEARS), so accounts will be centralized for 98% of people and the question about username is for now useless