They just don't work. I used to shoot at a range that was posted something like "absolutely no loaded weapons." They've had at least two negligent discharges on the sales floor, one from a concealed weapon that was taken out to fit it to a holster.
Most folks in the business do what they can, but we still have yokels come through now and then. At least once a week, I'll have a conversation like this:
"I need to check that weapon, sir."
"It doesn't have a clip in..."
"I need to check that weapon."
"It's not loaded."
"I'll establish that."
"Jerkwad sonnuva..."
and a live round ejects when I work the action.
Thing is, that's just a hazard of working with the general public. If anyone's ever come up with a solution, I haven't heard it.