Having had the opportunity to view security camera images on our local news channels the sights are ignored in holding the gun sideways. In fact, the perpetrator is not even looking at the gun but rather at the clerk, cash register, the display behind, or whatever holds his interest.
In many cases there is a Lexan partition which the crook is extending his hand over. In several cases, when the victim ducks down or moves aside, the gun is useless, as the gun hand cannot flex enough to bring the gun to bear. In several cases, this has proved fatal for the would-be robber.
Clearly these crimes are often not too well planned.