It used to be that way. Under the Carter administration, I believe, who probably did it in an attempt to further reduce the size of the military as well as lessening the amount we spent on maintaining it, in the seventies simply joining the military was no longer proof of your commitment to this country's core values. You were on your own, and had to go fill out the forms and apply for citizenship on your own dime, with no more consideration than that of any other applicant.
Less, actually, since I happen to know for a fact that they were handing out the questions and answers to the citizenship exams to the Vietnamese "boat people" so that they could get their citizenship without too much bother.
Thanks for the response and explanation.