Idk why people keep joining that bullshit instead of spreading out.

Probably because they don't understand how federation works. People are used to signing up for centralised services, so when they come to Lemmy because of a reddit post where someone said "I just signed up at lemmy.world, it's great" and then they install an app and lemmy.world is the first instance listed, they just blindly assume that is the official/main instance that they should start with.