They could, they could also more likely buy an 80% firearm lower that does the same, this is why the ATF under Biden cracked down hard on ghost guns, to the point that one manufacturer shut down entirely. I like to watch police bodycam videos when I'm bored, there's a LOT of people who have 80% or "ghost guns" as they call them, I don't think I've ever seen someone using a 3D printed gun. Luigi Mangione was a strange out of the norm exception, he intentionally did it that way.

In reality, a 3D printed gun is not reliable, the filament will melt and nobody wants to have a melted gun while in the middle of a shoot out with other criminals or law enforcement.