Just for interest- in many (most) first world jurisdictions, the sticker/menu price is what you pay, including tax and service fees.
Tips are voluntary and only customary for exceptional service, in a restaurant. You'd never tip a taxi driver unless it's Christmas in London and they go cross-country to get you to Paddington just in time for the train you thought you'd missed. ;-)
US tourists are liked (at least in their first few days in-country) because they give juicy tips.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
