They shouldn't be so afraid to penalise the team with the ball... if a players "milking" on the floor, instead of just repeatedly shouting it, penalise the player.
I will never understand why refs allow attacking players to flop around like a fish out of water, or hold the opposition to win a penalty, with no risk of punishment.
Tomkins used to do it in every tackle, and others started copying because he was winning penalties.