If you tell the players "Hey, I'll disregard up to +2 LA." then they'll probably all go out and pick +1 or +2 LA races; which is fine and balanced. If all the PCs have the same LA, then they might as well have no LA at all, since they're all advancing at the same rate anyway.

The problem comes in when 3 people want to play a human, and one wants to play a Feral Drow or some such.