It isn't, but that is the system you buy into when you eat out. Your ethical choices are to participate in the system by providing at least the minimum acceptable tip or not eat out. (Its a STUPID system, but the waitstaff does not deserve to be punished because the system is stupid. They are trying to make ends meet like everyone else. I'm going out with disposable income for a meal, I pay them. I also tip delivery drivers, cabbies, uber drivers, my hair stylist, my nail tech, and the kid who puts my friend's boat in from dry dock.) Personally I use the menu prices as a guideline. But I'm not tipping anyone who spends time serving me in a tipped position less than $5 no matter what the bill is, and I'll tip far more than 20% on a small bill - because the system is stupid.