If they had to pay their staff more, prices would be higher. If prices are higher, not as many people can afford to go, resulting in prices going up even more. When waiters can rely on tips instead of just the hourly wage, they are given the chance of getting a really nice tip from someone who is generous, resulting in more money than without the tips. By not tipping, you are relying on the generosity of others to keep the workers you aren’t tipping above the line. If you think they don’t deserve to be tipped, don’t go there, otherwise you’re being a mooch in the society you live in, even if it’s in a minor way.