While there's nothing wrong with pawn promotions, there's nothing like a checkmate without promotions, using the pieces already on the board. Sucessful endgames, especially with only a few pieces, requires a skill set many players don't have.
Most of my beginning and intermediate students get good at basic openings and middle game tactics. However, where I really have to work with them is with their endgame skills. Its a lot harder to checkmate your opponent with a Rook and a King than a board full of promoted Queens.
So much whoa it had to be rated by the ESRB.