Penalties for Pile Ups

Why is there no penalty for not getting off the pile when the referees call the play dead and are trying to get people to get out of the way so they can see who has the ball? I've heard that some horrific things go on underneath those pile-ups, and it always makes me mad that these players get away with just laying there. It's probably hell for whoever actually has the football. These jerks should be ejected from the game if they don't get up.