Where promotion to Queen might cause a stalemate but promotion to
a rook, for example, avoid the stalemate and provide enough
material to win the game.
Try something like Black B on f6,Black K on f4, Black P on g2 and
White K on h3 with black to move.
8/8/5b2/8/5k2/7K/6p1/8 b - - 0 1
Granted, the mate is actually shorter without an immediate promotion
but for those who cannot visualize 4 or more moves ahead, the
promotion is more intuitive.