I was told in the police academy That they had first seen it in soldier of fortune magazine, I believe they mentioned 1911's and BHP's that shooting like this, caused the muzzle to flip vertically, and since most people present a greater target vertically than they do horizontally, increased their chances to hit said target.
I could also see an advantage in exposing less of yourself shooting over the top of a car.
Now "gang-bangers" do get it from hollywood, as an emulation of their "idols". let us all pray they dont start watching Jerry Miculek.
the idea of doing this with a jennings to enhance feeding was valid, until the slide sheared off the rails and hit me in the chest. brass from my cz-52 shooting surplus ammo caught upwards of 10 seconds of airtime, going completely vertical, in one instance hitting the gun on its decent.