the over 25 thing is fairly common. They'll still sell it to you if you're over 18, but if you look younger than 25 they will require ID.
What difference does it make though, what kind of crazy person doesn't carry ID around with them?
ooh crikey, didn't realise we were living in Nazi Germany. Why the hell should I be expected to carry proof of ID around with me as a matter of course. If I'm applying for a loan or something I'd expect it but not walking down the street or shopping at Tescos.