I don't think it just happens w/ girls.. I checked ID's for a bar for a while in college, and hey, cute guys
just kidding. But seriously, the only time I wouldn't let people in was when they were trying to use the same ID for two people (at the same time) or they were SO bad that no one would let them in. I guess it was because I had one from the time I was 16, and hey, it's fun
The drinking age is too damn high anyways.. you can get drafted and killed for your country, but you can't get in the local tap for a beer... COME ON.