I'm not much of a gun enthusiast. I don't own any. But I certainly see the appeal of 3D printing a gun just to get it to work, because it's cool. The same goes for other things I think are cool, like jet engines, stirling engines, airplanes and multirotors, trebuchets, 3D models of fractals, complex gear systems, etc. I'd be interested in printing all of these things just as a hobby, and a 3D printed gun is no different. There's no reason why a gun is unique, such that I or the average 3D printer hobbyist would only be interested in printing one to commit a crime.