Why do gangsters hold their guns sideways?

Holding a handgun high and sideways is commonly used by stick up kids, the thugs who rob convenience stores. Experienced stick up kids hold the gun sideways when robbing a convenience store because it's easier to point downward at someone standing behind a counter. If they cower behind the register or duck to the floor behind the counter, all you have to do is raise the arm up and point the gun down. Try keeping the gun pointed at someone ducking behind the counter while you have locked elbows and an upright gun. I guarantee you'll find that it's much harder. It's not impossible, but in a robbery situation where seconds count, you would waste valuable seconds trying to readjust.

Another reason is that most thugs hold their guns in their beltlines. When they pull out their guns, they're already sideways. Sometimes when they aim they just keep the gun sideways.
 
Yes, holding a gun sideways is terrible for accuracy. But for stick up kids, accuracy is not a concern. For starters, the gun isn't there to kill; it's there to instill fear and make the victim give up their money. If murder were the objective of a robbery, every robbery would begin with a murder and end in a robbery. Why go through the hassle of shouting orders at someone who may or may not follow directions when you can just shoot them and take what you want? Simple. Murder isn't the objective.

Also, keep in mind: they're not pointing their pistols at people standing 20 meters away. They're basically standing directly in front the victim. Accuracy isn't all that important at point blank range .

Obviously, this doesn't reflect what every crook in the world does, just a small segment. But there are some semi practical reasons why it happens.

And no, it doesn't just happen in Hollywood. Sideways gun holding happens in real life (BTW, these are two of the dumbest criminals in history).