Question for you. Why would you even bother asking at all? If the person knows they have an illegal weapon or, even worse, plan to use it against you they are not going to admit to it. So even if you do suspect or have a good reason I'm not sure what you would gain. If they tell you the truth then, most likely, you had nothing to worry about to begin with. If they say no you still have to assume they are armed for your safety and basically ignore the answer.
This is what I've always wondered about any officer ever asking. Would be nice to hear a response from one.
This is my view as well. No idea why they bother unless it's to lead to more questions on differnet topics trying to troll for more?
I'm no LEO, but I'd think it would be worth asking. Just like when Leo ask if there are drugs in the vehicle or ask to search and people admit it or let them - Even when they know there is! I'd assume that every single criminal isn't a stone cold killer (or often times very smart), nor do I think most actually have the jevos (<balls) to use a gun even if they do have one. Just asking can't really hurt. Smart criminals will lie, others may not? Just an assumption.