Because we're nto going to call on citzens that way today. Any threat we likely face won't be here, and anything here would require more that your shot gun. So largely, the entire rationale no longer exists.given that they considered the militia to be "the whole people", i'm not sure you could argue that they were first looking to maintain a citizen army as an end in its' own right.
however, even if they did, why does that rationale no longer apply?
and it seems that if you feel that it does, the answer is obvious - get public support and amend the Constitution. then it will be your intent that we should hew to.
And I don't beleive anythign changes without an amendment. And all I would like to see is some clarity for today. No major changes on how we function, but clarity that might help end some of the debate.