Well, instances are all different, independent websites. As an admin, if I can't name a community whatever I want on my own website, I'm probably not participating in this ecosystem.
Plus, 1000 times more posts get posted to r/bigsub than you or anyone ever reads, and 10,000 times as many comments. It creates an environment where no one is actually discussing anything, and are just jockeying for attention.
You won't actually miss anything except for big vanity numbers by just choosing the community you like best for a topic and just... Ignoring the others.