I agree with those who have said that the problem is that the waitstaff are underpaid to begin with. Stiffing them on tips could lead to them taking home less than minimum wage. Keep in mind that in many restaurants, tips are split between the server, busboy(s), and runner(s) who bring the food out but don't do the actual ordering/service, yet people are generally only tipping based on how friendly/attentive the actual server was. What if the kitchen was slow or sent out bad food? That probably manifests itself in the form of a lower tip, even though the server had nothing to do with it.

The server already has an incentive to be nice and provide quick service -- their desire to stay gainfully employed. Pay them a decent wage and we don't have to do this Rube Goldberg gratuity dance any longer.