Pierce is the C's Leader. When he plays hard, all the C's seem to play hard. The other C's seem to think they have a chance to win the game when Pierce is going all-out so it's worth caring that much that particular night. The C's may or may not be good enough to make noise in the playoffs (assuming they make it and Ainge doesn't trade the Core Four) and have a slim chance at the Championship, but Pierce is the Celtics right now. Salute the Leader.