The other side of this is that if you've got, say, 55 friends that play a game, you need to make 6 requests to the server just to get the full leaderboard. No sane programmer would do that to themselves, so they'd just specify a huge value for the limit and be done with it. If nobody's using the default limit because it's a pain in the ass, it doesn't really make sense to even have a default limit.