They're not AR-15's or rifles, for one.
If they are automatic, then you need a special (expensive and very hard to acquire) license and very specific storage scenario to own one. It's not something a regular person can get easily. I don't think I have ever heard of a mass shooting (GVA def
) using a legally owned weapon of this nature.
(Further to this I don't know if you can explain a specific benefit to a potential mass shooter of automatic fire as a feature. It would take some training to use this feature effectively. Regardless, civilians don't really get to have automatic weapons in the US.)
They are probably semi-automatic. They use a handgun round and are for all intents and purposes a pistol with different ergonomics.
Yes, an anti-personnel weapon, but then, so is a handgun. I don't know how these are classified in terms of statistics but I cannot think of an incident that has used one. Even in semi-automatic they are expensive, and being bigger they're hard to conceal. Being chambered in pistol rounds they have less power than a rifle and so then what would a potential mass shooter pick one for? Kind of pointless.
As far as justifying their existence in the market, people like guns as a hobby. For the most part, the vast majority of people who would buy a weapon like this is are responsible people.
You can take that "do people need to do this" argument to ridiculous extremes, do they
need cosmetic surgery, do they
need imported cheese, private jets, luxury cars etc etc.
I mean, you're effectively arguing that you're not comfortable with someone enjoying something, and I dunno, can they apply the same argument to your life and preferences in return? Eh. They're not hurting anyone.
