>You stated that there are people out there who would use it, so your statement that "no one" would want to is untrue.
Huh? There is no evidence that anyone is using a 3D printed 7.62 weapon system to do crimes. Of the existing evidence, criminals overwhelmingly use conventional firearms. I'm not understanding your point. The would-be and successful assassins in the news the last couple years used standard rifles, ranging from 5.56 to .03-06 in caliber. I think you are assuming that criminals are less sensitive to equipment reliability than they actually are.
Let me put it this way. If 3D printed firearms were such a game changer, they would already be using them at scale. They are not, and these laws are part of a fundamental misunderstanding about how firearms function and how 3D printing technology works.