I'm a voluntaryist who would gladly see even state governments go away, but Virginia's Declaration of Rights, written well before the US Constitution, explains it very well:
Section 13. That a well-regulated militia, composed of the body of the people, trained to arms, is the proper, natural, and safe defense of a free state; that standing armies, in time of peace, should be avoided as dangerous to liberty; and that in all cases the military should be under strict subordination to, and governed by, the civil power.
It's almost funny, as someone who obviously was just brought up with this narrative to finally come to understand it - thanks for the elucidation. I honestly think that the official line from the powers-that-be over here has always been something like "Those crazy Yanks!". Over here we are thoroughly brainwashed into the idea of America as a zany but somehow flawed place. It has been surprising, over and over again, for me, to find elements of American culture displaying wisdom and understanding that is up there with any culture the old world has to offer. This approach to freedom, when looked at closely, is clearly the only mature route. And yet, like I said, in the UK people rarely, if ever, seem to say anything about it other than, as I have said, "Oh Americans and their crazy gun laws". We are like the farmyard dog that laughs at the free wolf because it has no collar and has to hunt its own food. We are kinda cute, but, ultimately, kinda domesticated. Not saying that's necessarily a bad thing. Depends how you feel about calling someone else "Master" I suppose. We claim to have given up on the "Divine Right of Kings" and yet there the Royal Family are and there is "Her Majesty's Government".