Originally <a href='http://www.sportsbookreview.com/forum/showthread.php?p=22940677'>posted</a> on 11/07/2014:

These people smile and act polite because they want your business and they want you to return. If they don't act pleasant you take your business else where and they know this. You paid these people to make and prepare your food; a fair trade. So giving them extra money for the hell of it makes no sense. If you want to give someone money who has done nothing to earn your business, give it to a bum on the street or to charity.