There are places out there which have sullied the idea of tipping. I have a Quizno's sandwich shop near me, and their sandwiches are good in a pinch. But they have a tip jar sitting next to the register, as if saying "give us more of your money." They didn't serve me anything like the servers at restaurants. They didn't come out to a table, take my order, and bring it out later. They just made my sandwich and rung me up. Other places do likewise, not being servers at all, they just simply have a jar there for more money.
The origin of tipping has it roots (perhaps in part) in the story of a gentleman named Dr. Johnson who would visit his local coffeeshop on some regular basis. He would drop a few pence into a box labeled "To Insure Promptness." Note these words spell out T-I-P with their first letter, hence the acronym of tip. The idea was to induce a hightened motivation in the generally listless attendants. These days it has morphed into simply supplementing a server's income, used more as a way to convey ones level of satifaction with the service.