The arbitrary gift of 15 or 20 percent of the cost of a meal to the server is ludicrous. Yes, tipping is designed to reward a server for good service. I almost always tip, and tip well if the service was prompt, attentive and friendly. However, if a waiter or waitress gives me poor service, I don't care how much they rely on tips for their livelihood. Unfortunately, too many have come to expect a tip and make no effort to earn one. I don't care how low their hourly wage is, if they want a good tip they need to give good service.