You're also looking at the left side of the rifle. Shooters tend to not like getting hot brass to the face.
As far as weapons that used cased ammo, it can also suck to be on the left side of a left handed shooter. Had hot brass bounce off their arm and land on the back of my neck. And stay there.
Staying in position and on target took a bit of willpower at that point.
Completely unrelated to all this, I think of osmething from the old Marvel 2099 series where they had widespread plasma weaponry and someone was using a shotgun. 'Why do you cock it?' 'Because it's awesome'.