America has a tradition of paying its workers poverty wages and counting on the pity of patrons to make up the difference. I don't care if you're a Brit or a Martian; when you're in a restaurant or bar in any country you should follow the local customs.
Although that's true in Israel where many waiters don't get any salary because they rely on tips, though nowadays, I think most restaurants, at least reputable ones, "guarantee" staff the minimum wage, meaning if they don't make it in tips, the manager agrees to pay them enough to cover minimum wage.