They do in the US, at least in Minnesota. (In some respects the US is 50+ countries in a trench coat... and probably not much else, ready to flash our flaccid little Florida at unsuspecting victims.)

They do in Germany

They do here in UK. It's entirely stupid.

In my local Lidl in Finland I was able to buy beer upto 2.5%abv without checkups, until about 18:00. The employee explained to me that during the day when they have more employees they let you buy it without checking, but in the evening they have less employees so less eyes on the self checkout.

Depends a lot on the country and sometimes even between the store chains within the country. At my local store you can't buy anything age limited at the self check-outs, they start flashing and beeping and you gotta get your stuff and walk to the closest real check-out. And alcohol free drinks, like beers wines ciders whatever, are treated the same as the original versions, limited to 18. Heck, even candy pipes (tobacco pipe shaped liquorice candy, quite delish!) is age limited as it kinda-looks like a pipe and you know, think-of-the-children.

one of my favorite "welcome to ____" experiences was when i moved to Utah. I went to the local grocer and bought some San Pellegrino. the cashier carded me. now i've worked retail, so [most likely] this was her first day (the POS tells you when to check someone's ID) or [i've learned not to overestimate Utahns, so also most likely] she somehow had no understanding of what i was buying. i somwhat bemusedly told her i'd show my ID to her manager. when the manager came over, i pointed to the bottles and told him the cashier wanted to see my ID.

i may have memory problems from time to time, but the look on the cashier's face when her manager told her I was buying water will remain with me til the day i die.