Question about buying beer?

well , i did work the door at a night club bar , and even if they looked old enough . it was policy to card everyone . because you can't buy booze unless you have your id on your person . so maybe its down to the store level on id for the purchase of booze , beer wine or hard stuff it made no differents to the management of the club . and that was back in the 70's and early 80's .