Also this is somewhat tangential to the guns thread, but something like a .38 snubbie would fit EASILY into one of those pockets and the officer wouldn't have any idea. And there are much smaller guns and weapons out there.

Is it likely that the guy standing in the middle of the parking lot is armed AND ready to use it? No, but on the same token it very well is possible and very simple requests like 'take your hands out of your pocket' are very reasonable and there has to be a certain amount of authority to back that up (i.e. it has to be a legal requirement and not just a kind request).