I sincerely appreciate you bringing this fact up. After reading your post, I did some of my own research on the subject. I incorrectly thought that automatic weapons were illegal in the U.S., but they most certainly are not. If you have the money, which, obviously, the Vegas shooter did, it isn't that difficult to get a machine gun.
http://thefederalist.com/2017/10/02/actual-federal-laws-regulating-machine-guns-u-s/
I really don't see the purpose of automatic weapons being legally available to civilians. We now know that reasonable gun regulations are perfectly legal and constitutional, as they do not infringe a person's right to bear arms. The 2nd Amendment certainly does not guarantee civilians to be able to purchase every weapon, if they can afford it. It merely guarantees our right to own a weapon. If you are able to buy a gun, your right to bear arms is not infringed according to the SCOTUS. There is no requirement to make all firearms available.
So, that means that there must be sufficient reasoning to make automatic weapons available to the public. Can you provide your reasoning as to why you think it is necessary for the public interest? What makes automatic weapons necessary in addition to semi-automatic weapons? Often I hear the slippery slope argument, but that is obviously fraudulent reasoning whenever it is used, as it doesn't address the actual question ... it is merely a side-step to avoid even talking about it.
So, are you saying that it being used as a hobby is reason enough to make it available to civilians? What comes to mind is drugs. Drugs can be used safely and in good health. I know many people from my younger days who used drugs at concerts, were safe, healthy, never got addicted or anything, and stopped using them when they got older. I know many, many successful, honorable, dedicated and driven people who smoke marijuana regularly. Yet, federally, it is the same classification as heroin, while automatic weapons are not. Actually, cocaine and crystal meth are schedule 2 drugs, but that is beside the point. Are you in favor of legalizing marijuana federally for the same reason? That some people are able to use it safely?