Ligit question. Some folks may be younger and not have had the time to think through appropriate responses.
An acquaintance, "Why would I carry a gun?"
A friend, - ALL of my close friends carry = "You like the new holster?"
Anyone else, "Excuse me? I didn't catch question." with completely stupid look. If they ask again. "I have a large cell phone." Walk away or if trapped at a party, change the subject. What do you do for work? Are those your kids? etc. (People, for the most part, like talking about themselves.) If OP presses, return the question. Are you? I will never give a straight answer, unless required by law.
Bottom line: If you aren't a close friend, it is on a need to know basis.