Waiters do a lot more than go get your food. They have to make the tea, bring ice out the back in 20 pound containers, refill ketchup, dressings, salts, put the food in portion bags for the cooks, clean the restaurant, sweep, bring dishes from the dishwasher up to the front, all the while, serving food, creating tickets, ordering drinks, making change, running food for other busy servers, refilling your drinks, replacing essential sauces in the back that they use for tables such as Salsa, queso, butter, depends on the restaurant.
That is for the Restaurant's benefit. That is apart of their job description. I tip and don't really have a problem with it cause I'm just used to it now. I have always wonder how it has been made mandatory when I could easily get the stuff myself. I like to tip for things that I do not have the capacity to do when I receive a service.