When I was in, we also were able to consume on post at the E-club. And the bars in the adjacent cities/towns overlooked under aged soldiers being served. Wheather for economic or patriotic, reasons are unknown. Also at the time the legal drinking age of my home state was 19.
I also agree, if you are old enough to volunteer to be a mobile bullet stopper and serve your country, you should be old enough to walk into a bar and get a drink. And to be able to purchase a handgun.