Because unconstitutional laws prevent me from haven an M-16.
In most states in this country it is legal to own an M16, an M60, and even a .50 cal BMG. The feds don’t care care as long as you comply with the paperwork, pay the $200 and get approval. Sawed off shotguns, ditto. Gernades, ditto. Alhough with a $200 tax per gernade, those aren’t on my shopping list.