Because the other tourney's are that way and if they do it 6v6 eveyone can keep the same teams.
That is correct...
The idea is that you can bring 5 buds, or make 5 new friends at the event, and always have a team. It would suck to have 2 tournaments where you are on a team of 6, and then have 1 player get bumped from before the CS tourney, and not have a team to play on!
That was the idea behind it.