It's true that you can make your own subreddits, and of course you can keep loading more pages, but the cutoff rate is pretty severe. A few non-default subreddits (like /r/Frugal) do have sizable power since they're well targeted, essentially functioning like mini-reddits.
HN is similar, but since they go out of they way to stay obscure, any increase in traffic is practically accidental.