A rare instance in which I wholeheartedly agree with George Will

Drinking Age Paradox:
Among college students, drinking has gone "off campus and underground," increasing risks while decreasing institutions' abilities to manage the risks. ...

McCardell thinks that, on campuses, a drinking age of 21 infantilizes students, encouraging immature behavior with alcohol and disrespect for law generally. Furthermore, an "enforcement only" policy makes school administrations adversaries of students and interferes with their attempts to acquaint students with pertinent information, such as the neurological effects of alcohol on young brains. He notes that 18-year-olds have a right to marry, adopt children, serve as legal guardians for minors and purchase firearms from authorized dealers, and are trusted with the vote and military responsibilities. So, he says, it is not unreasonable to think that they can, with proper preparation, be trusted to drink.
I currently live in the vicinity of a number of colleges with large undergraduate populations. Many evenings when I walk back from work through the park I see the college students congregate in the bushes to drink beer. While there's nothing necessarily wrong with that, every morning when I walk by again I see the mess they leave in part because they don't want to be caught with evidence once they emerge from the dark. Luckily, there's a bottle refund here so the homeless pick up the bottles and cans throughout the day before the process begins anew the next night. The fact is, these students will drink regardless of what the law or the college rules say. If only they'd be allowed to go to any of the copious bars in this area, it'd be so much safer for them and for the park's waterfowl.

Oregon used to have some of the most insane liquor laws while I was growing up. Things have changed there since the late 80s, but I remember the days where certain musical events were off-limits to me because the venue had a liquor licence that didn't allowed "minors" to enter.

It's just stupid to think that we can effectively enforce a 21 year old drinking age and to imagine that it's actually doing any good whatsoever.