American server here. Yeah, if I provide shitty service, you shouldn't have to tip me. Personally, as someone who has served and has gotten paid less than 'minimum wage' (service industry is different in some states), even if I'm the one getting shitty service, I leave 2-3 dollars on a $60 bill. I understand shitty days and putting up with hungry people. But it definitely is a culturally economic thing too. So if someone provides excellent service, or I see them as an extremely hard worker toward the guests around me, I leave them extra. Although I definitely agree that the tip should be included in the menu items and servers should be paid more than $15 (min wage is $9 where I live) in the more populated cities.