In American restaurants, gratuity is not included in menu prices. It is left up to the patrons to leave what they think was deserved – 18-20% is standard these days. So, I experience a vague irritation whenever I see “gratuity included for parties of X or more” on an American restaurant menu. It smacks of a lack of trust in me to treat the server with the respect they deserve. I assume that policies like this spur from being wronged in the past. I understand that thinking and know that it happens everywhere, though its not always as obvious.