Elizabeth Gunnison Dunn, writing for Esquire:
If you are of the belief that a tip is an optional kindness you’re doing for your server, you might be surprised to hear that you are not in France. Here in America, the practice is voluntary only in the legal sense of the word. You are not technically stealing if you don’t tip the customary 15 to 20 percent, but that’s probably the best that can be said of you. The tip you pay is a sort of wage: federal law allows tips to be used to make up the difference between a server’s salary and minimum wage, meaning they can make as little as $2 to $3 per hour from their restaurant employer. Tips are absolutely depended upon to make up the shortfall.
When you leave a bad tip, you are docking a person’s wages. This may either be because you’re confused about what’s expected or because you’re an asshole, and you really believe that your sea bass arriving lukewarm is justly punishable by making it a little harder for the guy who brought it to you to pay his rent.
Dunn goes on to smartly point out the flaws in the tipping process. Consumers are forced to subsidize the incomes of service industry employees because the employers (backed by federal law) refuse to pay a livable wage. If that is the reality of service industry margins, fine. But that further illustrates the stupidity of tipping. Instead of simply adding a service line-item on bills, employers leave it to confused, math-challenged, and often immature customers to decide the service fee. Not only does that eliminate fairness, it leaves employees susceptible to the sexual and racial judgements of their customers. In short, it’s 2013 - tipping as currently constructed is dumb.