Well it is important to know who is at which level for many different reasons - and having it as a pawn-knight-rook makes it really simple to know who each person is.

Some examples of how I use these different levels:

1. When I'm inviting people to my fellowships, I know to only invite knights and rooks and not to invite pawns.

2. When I'm starting my tournaments, if it is a limited "5 person" tournament - I now know to look at all pawns and rooks to make sure they have enough games open before starting the tournament - so they don't get removed and the tournament does not get deleted.

... this is a couple of quick reasons why the current system works well for me - I find it very handy to know what lever a person is really quickly..... and to change it would be a pain to me, and I'm sure to many others also.