I'm not sure if that's what it shows. That's the same pattern you see on all kinds of sites: most Wikipedia edits are done by a handful of users. There's a small core of ridiculously-active people answering questions on Stack Overflow. Of the millions of people who try streaming games, a few are wildly successful and account for a significant share of all watched streams. Reddit, with it's super-submitters, seems to fit right into that pattern.