In the US you need to be 21 to drink beer or vote, yet 18 is fine to join the army, meet new and interesting people and kill them.
Almost all countries, including Germany, also impose an excise duty (harm tax) on beverages like beer, but the amount of tax varies considerably by member state.
It might be possible to order beer from some EU countries to others, but for example certain Nordic countries still maintain a state alcohol monopoly which practically makes it illegal for private consumers to buy alcohol online even from another EU country (more precisely, it makes the bureaucracy for selling alcohol so complex for the foreign retailer, that they just refuse delivery to these countries ..)
You can also safely ship liquor in the U.S. I like to ship back liquors from distilleries, but want to avoid airline baggage fees so I ship them via a shipping service. The booze has always come through fine.
Also in the U.S. you can vote at 18 (in some cases you can even vote at 17, as long as you'll be 18 by the first Tuesday of November of that year).