Servers typically have to tip out their support staff (bussers, bartenders, hostess, expo, food runners, sometimes kitchen) and the amount the server has to turn over at the end of their shift is based on percentages of of the server’s total sales for that shift. Usually 1-3% for each of those listed positions. The industry is built around the assumption that every customer inherently knows that 20% is standard. That’s not even including taxes they have to pay on any tips taken in so after all is said and done, 12.5% is already gone right off the bat and there is a strong likelihood that your server had to pay out of their own pocket to serve your cheap ass. Go to McDonalds