Two possibilities: (1) a moron who didn't have enough cash for anything else; and (2) a moron who counts on the deterrent effect of having a firearm. Note that the two are not mutually exclusive.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman