Copyright arose initially as a way of imposing government control over the disruptive technology of printing presses. Patent may well be the tool used to impose control, governmental or quasi-corporate, on 3D printing.
And if you support gun control, for example, *and* get excited about the possibilities of home printing in metal or some more durable material, you should start thinking about how you control a device that can be used to build unregistered copies of a device you don’t even know about.
Because there will be some sort of regulation. Pretending otherwise just leaves a tilled garden for noxious weeds of special interests to regulate.