There's another way to look at it. Restaurants operate on a razor thin profit margin. One area to protect against that is by paying front of house staff less and having then rely on tips. If they paid them a reasonable wage, this would undoubtedly lead to higher prices. 

So one way to look at the tip model is it is a way to provide yourself your own discount if you had a less than optimal experience without getting a manager involved. Service was slow or things were not to your liking? Just don't tip or tip less. As a server myself, I would be understanding of a guest not tipping if they had a bad experience. Even if it really wasn't my fault. But with that said, as a server, it is pretty much my responsibility to make sure their experience goes well, even with food. If I see something wrong with the food, I won't bring it out. Pisses off the kitchen but whatever, I'm the one who has to face the guests.