I was raised similar to Tyler, my brother and I were both allowed to drink at home at about 17 - 18 years old and we were not allowed to leave after we started drinking unless it was walking. We did have honest parents that were pretty open with us when it came to frank discussions about alcohol and drugs and didn't just demonize these things as "forbidden". Like Tyler, we didnt run out of the gates chugging PBR by the gallons when we turned 21, this is when we actually started to get a taste for good liquor (s.m.scotch, top shelf tequila, etc.).
I just dont think most 18 year olds are mature enough or have had the support structure in their lives to cope with the unbridled availability of alcohol. I also do not think most 18 year olds are mature enough to deal with the effects of war either, some are and they join the armed forces (and they should be allowed to drink when taking on that kind of responsibility).
They say that 40 is the new 30, well I think 18 is the new 15... the 16 year olds that were fighting WWII seemed far more responsible than the typical 18 year old of today... the 19 year olds that fought in Vietnam were far more responsible than the 18 year olds of today... having everything at your fingertips and not being expected to work a job until you are 23 is a far cry from the days when quitting school at 16 to work at the local mill to help pay for your familys farm was common. I think they are far more desensitized (from the abundance of media) but still extremely immature in the realm of responsibility.