there's an awful lot of ways to make a slug of metal fly out of a handheld machine at very high speeds. Some of them require gunpowder.
I'm not in the slightest interested in making a gun, when I could be making a bicycle, or a stepladder, or guitars, or tractor parts, or robot bits, or jewelry or any of a billion other things instead.
It's a file. One of many. and trying to keep that file from spreading will only make people try harder to spread it.
At one time there was some sort of control on this, because it was too hard for even the above average person to make.
Only master craftsmen could make a gun.
That simply isn't true anymore.