A few years ago, I was sitting at a bar in Vegas having lunch and the guy next to me finished up and paid his bill and he was "Whut?!" when the bartender grabbed his card and headed off. I must say, I just got back from Europe and the near universality of just tapping a card on either a portable terminal or at the bar with no worried about manually adding on service charges (though in the UK there is usually an "optional" charge added on for table service) is quite streamlined.