I find it really bizarre - before I was of legal drinking age, I didn't get carded, ever (and went out and drank a fair bit from 16-18). I visited the US several times while underage, and didn't get carded once. It was only when I became of legal age to do pretty much anything that I was first carded - and it was a real surprise! I don't mind the policy, I get the reasoning, and in an airport it is utterly fine as I always have photo ID with me, but if I pop round to the store to buy wine, or am out somewhere away from home, I often wouldn't have any photo ID with me (not driving, don't need my licence is my logic), and then it would bug me and common sense should prevail. As it happens, I haven't had an issue, but I do have to remember to caution UK friends to bring their drivers licence with them (so they don't have to carry a passport) when we go places in Canada and the US for that very reason.

It is becoming more of a thing in the UK - my mother and I (both most certainly legal to drink) were buying wine for dinner along with the rest of the shopping, in a store we don't normally visit. My mother got asked for ID (which she doesn't have as her drivers licence is non photo) and in the end I had to buy the shopping because I had my Canadian licence with me (which also required a supervisor as it 'looked funny' [small town UK].)

I bought booze in Target - they looked very confused and called a supervisor. I swear the person behind me thought I was trying to buy booze underage by the disapproving looks I got, and the jaw open when I walked off with the booze, with no licence scan!