>unlike buying a product a good service means a good tip

Why? Why isn't the service built into the price? What even is good service?

If I go see a psychiatrist or physician and they make me feel better, offer me coffee, and make me feel at home, then you can say that's great service. Yet no one tips their doctors. We even find that unethical as a society. The reason we tip wait staff is because we know they get paid shit and are guilted into doing so.

We tip waiters 15 - 20% just for doing their job. Rarely is the service "exceptional", because by definition, it can't be.