I paid for the pizza. I paid for the delivery. Somebody delivers the pizza that I paid for. Why is more money required from me? What am I missing here?
In a restaurant, I pay for the food but I don't pay directly for the waiter. That's why I have no problem tipping in that scenario.
But give me one good reason to tip a pizza guy other than he doesn't make much money and I do. That's the only reason to tip and I have a big problem with that.