Cho'gath's E, WHY CAN IT BE TOGGLED???

After playing Cho'gath throughout season 2 and 3, I've found little to no reason for his E to be toggled off. It does not consume mana when toggled on, and does not provide any sort of benefit for toggling it off. The only scenario I can see that his E would be better toggled off is either when you are attacking minions early game and do not want to hit the champion behind them, angering the minions and causing them to attack you. Or when you are attacking a turret with a champion behind it, causing the turret to get mad at you and attack you. Besides those two things, I can see absolutely no reason for Cho'gath's E to be able to be toggled off. I have actually toggled it off by accident in the middle of a fight many times due to me playing champions whom I use E alot in combat for. It seems a bother to me is all.