Why do you think that would be the required response, or even a preferable response? You see that in movies, not so much in real life.

I imagine this is what untrained and knowledge lacking people associate with a typical response, because that's what they see on their TV. They are uninformed, and wrong. Besides, those head shots are usually taken from more like 50 yards out, weak handed, instinctively aimed (no sights), while riding on a horse going in the opposite direction. The impact of the shot usually throws the bad guy back through the air 30 feet, bursting through a one inch thick plate glass window that suddenly appeared out of nowhere. Then he explodes. Then the good guy proceeds to make 34 more of those same awesome shots, using a handgun he never reloads. That makes slide racking and brass ejecting sounds, even though it is a revolver. Then he pulls out his knife for more carnage, which obligingly goes "zzziiinnnggg!", apparently because he simply touched it.

Unfortunately, people believe, and base their opinions on stuff like this.