I think a fundamental issue is the difficulty in re-creating an authentic fight experience in the studio. Some arts go to great lengths to make the training as close to a battle or fight scenario as possible, but there are always points of stoppage, padding on the body, blunting of the weaponry. At most it is ritualized combat. And yet even the most advanced Delta-force level soldier faces these same limits in training. It takes years to achieve the advanced levels of combat training in the military, and it is a constant learning process for them as well.
Be nice, until it's time to not be nice.