ID? What the %$#%$?

Okay, I always thought that you only needed ID to buy alcohol at the age of 15 and so did you right? Wrong... After a long day of scraping, sanding and painting at the old house, we came home saturday evening, where dinner was already served (thanks Bev), we finished dinner and went out to pick up a movie and relax a little bit. In the videostore, we decided, in a moment of sheer brilliance, that a beer would go down very well, so we stopped at Albertson's on the way back. And now for the fun part; we weren't allowed to buy the beer because I did not have any ID on me. I'm f*****g 24 years old and I was with my uncle who is 37 and did have ID on him. Now should I take this as a compliment or be totally stunned about the madness in this country? You decide... Just wondering about the consequences of this everyone-in-the-group-of-people-of-which-one-is-buying-alcohol-
should-have-ID-showing-he-or-she-is-over-21-even-it-is-obvious-
by-using-your-eyes-and-lump-of-nerve-cells-embedded-in-the-
skull-more-generally-known-as-brains-policy. Does this mean a family doing their weekend groceries can not bring a bottle of wine if the kids accompany them to the grocery store? I am truly puzzled with this... So we went to another store and I waited in the car like a 14 year old sending out his big brother for a beer... Going through al this trouble the beers tasted extra well while watching Oceans Twelve, which I had already seen on the plain but this time I could actually hear what they were saying which came in very handy in understanding the plot... Still that one sentence "can I see your ID please, the both of you..." I don't think I have ever had someone asking me this in an alcohol related context.... Weird.