Incentives matter, but a percentage based tip is simply the wrong incentive. It is the same amount of work for the waiter if I order $10 spaghetti and a $30 bot

Incentives matter, but a percentage based tip is simply the wrong incentive. It is the same amount of work for the waiter if I order $10 spaghetti and a $30 bottle of house wine, or if I order $50 steak and $300 bottle of Champagne. Why should s/he be rewarded for my own choices, based on no input or effort on his/her side whatsoever?!