Fully auto is overrated and an inefficient way to use your ammo. It drops the accuracy of the weapon significantly, so even though you're shooting more bullets per second, it's unlikely you're hitting your target with any more precision (more often than not missing completely) than you would by simply squeezing the rounds off manually at around a second at a time.
So, it might actually save more lives to have fully automatic weapons legal and semi auto's under tight restriction instead....