I didn't drink until university, so I never had ID. When I started drinking, I never got IDed, generally - because I was 19/20, over six feet tall with a receding hairline.
(This didn't stop me getting IDed for paracetemol once - punchline to that being that it was only because I was buying two boxes at once!)
Anyway, I had to get ID eventually because they kept throwing me out of places. I literally once got thrown out of somewhere that had already served me because one bartender didn't bother to ID me and then the barmaid two hours later did.