Well, that is pretty much how we would rationalise the drinking age too. It seems crazy to ban the demon drink but allow young people into far more potentially life-threatening situations.
Booze is pretty expensive all over Europe, even in wine producing countries. I've never been able to figure out why Bath Ales which are made just down the road are so expensive - but there you go. Booze prices are out of the reach of most pockets in Scandinavian countries because their short days encourage addiction to drink. The Brits are simply incapable of moderate consumption either at home or elsewhere, and the government is tackling so-called "binge-drinking" through raising prices. It seems to have worked in Scandinavia.
I knew the bit about Scandinavia, that is why they all love going to Copenhagen where the taxes are cheaper. But that also goes for just about any consumer good there, but especially alcohol. NH's beverage industry has gone through a resurgence in the last twenty years with the craft brewing movement. We have at least 30 breweries in state now and at least as many vineyards where we were just down to the Anhauser - Busch facility in Merrimack where the Clydesdales are. Flag Hill started as a vineyard and expanded to distilling.
As to the "tiered adulthood" setup, that was largely political. Legal adulthood was constitutionally set at age 18, and like I said the drinking laws were largely set at the state level up until 1984
. After that sales were standardized across the country.