I can see the point in IDing people for alcohol and cigarettes. Well, they could harm your health (and depending on your perspective, others' too).
However, when I walk into a shop, and try to buy some car shampoo (the stuff you mix with water to wash your car), I don't expect the woman behind the counter to say "I can't sell you this. Have you got any ID?"
For the first time in a while, I was actually gobsmacked. You see these things in the Daily Mail, but actually getting asked for ID for something as pathetic as car shampoo is just shocking. What on earth am I going to do with it other than wash my car?
I have a full driving licence, it's quite clear I can drive and chances are I'm going to use it to wash my car.
Is this jobsworthiness, or is it actually getting scared that the police might sue you because I drunk a bottle of car shampoo, and you just happened to sell it to me?
Yes, this actually happened to me. I got IDed for car shampoo.