We (the responsible R/C helicopter community) have been asking, in fact begging, for regulation for some time now. Even going so far as to have pseudo-regulation via AMA. Unfortunately the FAA has continually put the issue on the back-burner....
I'm aware of this. Sadly, this won't change until there's money involved, like Amazon's recent research on using quads for package delivery. These regulations are strict and hard to change, but, again, there's good reason for it.
Also, the analogy of radio-controlled cars is absurdly non-sequitur as cars are 3,000lbs of steel/aluminum and multi-rotors are 27 oz. of plastic/carbon fiber.
The thing is, you don't need a lot of mass to damage something that flies. A RC car can wreck havoc if stepped over by a car going 70MPH on a highway, just like a quad can do even more damage if sucked into the jet intake of an airliner / helicopter. Or the propeller / attack surfaces of a small airplane - incidents with birds, for example, are sadly common.