Because the leaderboard has positive and negative sides to it.
The negative sides have to do with the people that think that HN is all about 'being in the top 100'.
The positive side is that you can see fairly easily who are the people that have spent a lot of time on the site, in other words who is here for the long haul and who is passing through.
On /. you get a similar feeling by looking at people uid#, here we don't have that so the leaderboard has some of that function.
> Rude people are rude people. If they can't complain about your karma they will complain about your socks.
Ah, but they can't see my socks :)
> My advice is to ignore them and carry on. Don't take criticism seriously unless it's serious criticism.
It gets a little tedious after a while and the negative returns from being on the leaderboard seem to outweigh the positive ones, hence the request.