Economy Talk

can someone explain american tipping to a confused brit

Mate's just back from the States and he's traumatised. Says he got asked for a tip on a self-service screen. A screen. Where he poured his own drink. Options were 18, 20 or 25%.

Over here you leave a bit at a restaurant if it was good and that's about it. Driving a bus I've never once been tipped, though a lad did give me half a sausage roll once.

Americans, is this normal for you? And everyone else, how does it work where you are?