Question about buying beer?

Some stores, and especially the larger corporate ones have it programmed into their system, to lock up for any age required product. The store I use to work at has gone to scanning the ID. They're doing this to protect themselves from fines, and to protect their liquor, tobacco, etc. licenses. I believe the reason for the scan is to prevent a cashier from doing what was mentioned above. If they look of age, just punch a number in. I know personally of one instance where that happened, and got the store busted for selling cigarettes to a minor. Cashier's first day on the job, and the trainer no less, told him to just punch a number in. It was a sting. 17 year old kid, that looked in his 20's.