@SputnikBear
Maybe not the world or the youngsters, but the licencing laws changed in 2003, introducing harsher penalties for those actually serving the alcohol as well as the licencee. Poor training and the laws themselves being a bit open to interpretation lead to a lot of misunderstanding. Most servers err on the side of caution because we've had the fear of God put into us and threatened with £20,000 fines and up to 6 months in prison if we break one of the laws. And they are checked upon regularly with test purchases by trading standards and the police. Fail one and you don't forget it, trust me.
Long gone are the days where as bar staff, we could turn a blind eye to someone not quite 18 behaving themselves having a few beers, even if with their parents. I just don't risk it now because it's not worth £20 grand I don't have or a prison sentence if I am caught. I always ask for ID if in any doubt, and no ID no alcohol, even if that's half a cider with a Sunday lunch.
Some places have an over 18 only policy because as I said poor training and understanding of the laws leads to misinterpretation. Someone further upthread said 14, and invariably on a thread like this someone will think it's as young as 5, then the misunderstanding about drinking with a meal - they can be under the impression that because an over 18 can buy it for a 16/17 year old, that this can continue after the meal, it can't. Easier and safer for the licencee to just say over 18 only, and ID to prove it.
So most under 18s unless they look over 25 (all licenced premises must have an age challenge policy) or have excellent fake ID (not the dodgy ones we used to fake on the ancient school computer 🤣) they won't get served going into pubs and clubs these days.