The argument could be that a QB should ground it every time. Think about it. What is the penalty for intentional grounding? They spot the ball at the point of the grounding and you lose the down. What happens if the QB does not ground it? He gets tackled at the spot where he could have grounded it and the down is over, move on. Technically there is no difference / penalty for grounding. You get the ball where you would have been tackled and move on to next down.