When you go to /c/books on your server, you don’t see an agglomeration of all /c/books on all servers of the fediverse. You only see that server’s /c/books, if it even has one.
What prevents from visiting /c/books@anotherserver?
Genuinely asking, because this is one of the core concepts of Lemmy and federation
I guess that's the same for most of the userbase. Which is probably why switching to a more spread language could increase the number of contributors.