Do you know why they took the panic buttons out of banks? Because the guy with the gun looks for actions like that and will shoot you. Now, lets assume that the guy robbing the pizza place isn't a total dumb-ass (which he probably was...or black, or something). you think you could reach under the counter and get your weapon out, load it, and shoot before he can pull the trigger? I don't think so. The guy's gonna be jumpy he'll probably shoot you if you sneeze.
I've never been held at gun point because people in my country don't have guns. In my city there has been one gun homicide in the last couple dozen years, and it was done by an American.
Or it could also be because I have one of these at work...
http://soldiersystems.net/2011/10/23...ts-c8-carbine/