You can't afford 15% on your bill, maybe you should have eaten somewhere they don't hire people to service to your dining needs. I never feel entitled to someone else's money, that is just asinine.
Most other professions, pay at least minimum wage or more, your usually not dealing with cranky hippos who think your entitled to the money they tip you. Most of the people I know, and myself only really harbor resentment towards people who are dicks, and then refuse to tip you. I could've been surly and foul mouthed back at my customers, but I would have been fired. So in all honesty, if you can't pay the tip because you are financially incapable of doing so that is fine; but then again you probably shouldn't have gone to place where they hire people to service your dining needs.
If you don't want to pay a tip becasue you think it an outdated practice going to when servant worked for room and board, and that was their pay. Just eat at McDonald's. No one is forcing you to go eat an actual restaurant, where their hosts actually bring food to your table instead of just ringing up your burger and fries.
If you work in a Restaurant like Flemming's, or Daniel's your base pay will be higher than if you worked at Claim Jumper or Red Robin; Becasue you provide excellent customer service, and people
WILL tip you a gracious amount if you provide premium service. These places wont hire people who don't have serving experience becasue they don't their staff full of snot-nosed college students want to scrape a few buck together to buy weed for the weekend party. I can't say we didn't do that while working there but we provided excellent customer service and were rewarded for it.
If you don't want to be rewarded for your time, effort, and hard work; I will gladly take your tips.
So there is a very simple solution to your problem: Eat fast food.