The drinking age there is 18, but ages 16 + 17 can be served, with adult family members and with food.
I think the 21-year old age, in addition to being absurd for all the reasons cited, also prevents normal socialization around alcohol and promotes drinking in secret and binge drinking.
Yeah, forbidden fruit tastes better. There was some child shrink in the 70s that preached the way to get your kids to read the stuff you want them to is to put it on a shelf they have a hard time getting to, make it SEEM forbidden. Not sure they were totally right but it’s worth thinking about. My period of heaviest drinking was right before I turned 21, once it got legal it wasn’t as interesting. And once I got access to legal alcohol I lost interest in illegal drugs, just wasn’t worth the hassle.