Well this purpose is firmly stated in the amendment.
Anything on God’s green earth can be abused; it is up to America to keep enough vigilance on itself not to do that, including letting the private sphere be the guardians of the standards. Doctors do not need to pass government examinations to be permitted to practice; it is enough that they pass the examinations of universities that have a cross-accreditation system.
It’s simple human nature to push the envelope, to never be satisfied with the status quo. Once you concede that the purpose of the 2nd Amendment, which you have apparently done, is solely to establish militias, you have given those who demand universal gun confiscation all the evidence they need to begin the great grab. An excess of 20,000 gun laws already on the books, and still cries for more, should be instructive. If I’m wrong about your take on the 2nd, let me know.
It’s not, has never been, about militias. It’s about the existence of a God-given right, the purpose of which is to stop just the kind of all-encroaching government you seem to embrace.