Realize that unlike the other things you state, guns are unique in the sense that some people collect guns and NEVER shoot them.  An avid collector may have in excess of 100 firearms registered to them and only shoot a few of them on a regular basis.  There are also firearms trainers who NEED several models of firearms to properly conduct their safety courses.  For example, a NRA Pistol Instructor should have at least 3 firearms to properly conduct a class.  1) Single action revolver 2) Double action revolver 3) Semi auto pistol.  Keep in mind that it is common practice for instructors to take a variety of handguns to the range so students will have a selection of firearms available.  Also, many instructors are certified in multiple disciplines (rifle, shotgun, black powder, etc) which would mean multiple ownership of those other types of firearms. 
Note that the firearms owned by firearms trainers are properly acquired and registered, AND not used to shoot people.