This is well-plowed ground, but worth going over again. Reynolds makes a key point about what it means to be 18:
Along with joining the military, 18-year-olds can vote, marry, sign contracts, and even take on a crippling lifetime burden of student loan debt in pursuit of an education that may never land them a job. Yet we face the absurd phenomenon of colleges encouraging students to go into six-figure debt—which can't be discharged in bankruptcy—but forbidding them to drink on campus because they're deemed insufficiently mature to appreciate the risks.
That is an odd way to treat people. And there's more, including the key point:
Defenders of the status quo claim that highway deaths have fallen since the drinking age was raised to 21 from 18, but those claims obscure the fact that this decline merely continued a trend that was already present before the drinking age changed—and one that involved every age group, not merely those 18-21. Research by economist Jeffrey A. Miron and lawyer Elina Tetelbaum indicates that a drinking age of 21 doesn't save lives but does promote binge drinking and contempt for the law.
More than anything else, that's always been my largest problem with the drinking age change, which took place in the 1980s. We have in place a sort of 3-year Volstead Act right of passage built into our society. We also end up seeing people drink furtively and in large quantities, which is precisely the wrong way to go about dealing with drinking.
I don't drink much any more. I have had a number of friends and associates who have battled the bottle over the years and it's easy to see the pernicious effects that alcoholism has. No one disputes those things. But I do believe this: we'd have less problems if people learned how to drink the right way, in a social setting, with the supervision and support of peers. You're a lot more likely to get into trouble if you're pounding drinks out on an abandoned highway than you are in a tavern.