I believe I speak for all delivery drivers when I say that there's only so much quality service to go around. This means that we must prioritize. The chief criterion for deciding who gets the best service is quality of tip. That is to say, if someone is a known non-tipper, I am going to be more likely to show preference to another who does tip. Obviously, this does not mean that I will not provide service to a paying customer who does not tip, but I might for example visit a tipper, if you will, before I would a non-tipper, regardless of actual order. This is because I'm not in this for my health, or even chiefly for the hourly wage. Were that the case, I'd be at a different job making more per hour. I do what I do for the ideally substantial supplemental income obtained from tips. I'm not saying that if someone doesn't fork over tons of cash on top of the cost of the order I think any less of them. But at the same time, I feel that making a check out for $20 on a $19.96 order does not constitute a tip -- it's just an attempt to simplify balancing one's checkbook. Service workers, like anyone else, appreciate being appreciated. Another important thing to remember is what goes around comes around.