Why do we tip? If for a fare wage, does the server deserve less because I ordered a salad instead of a steak? If for service, what is 'good service'? Can you

Why do we tip? If for a fare wage, does the server deserve less because I ordered a salad instead of a steak? If for service, what is 'good service'? Can you quantify it? Do you even want it to begin with? Perhaps the next time you're about to sit down at a restaurant you should request the 'zero tip' experience. This should give you a lower bound from which to judge off of, if indeed you value the 'service' enough at all.