The studies referenced in this article say you are wrong: Managing Tips
A study from 2000 said the same thing, but you can only get to the abstract on the net: Relationship between tipping and service:
Numerous studies have found that tip size is only weakly related to service quality. Bodvarsson and Gibson recently challenged this finding—criticizing previous research and reporting that consumers say they would tip substantially different amounts with different levels of service quality. This paper presents a critical response to Bodvarsson and Gibson’s article. Contrary to Bodvarsson and Gibson’s claims, the weakness of the tipping–service relationship in the existing literature is not just a reflection of restricted variability in service ratings. Nor is it attributable to other methodological problems with service ratings. Furthermore, the data from Bodvarsson and Gibson’s role-playing survey is suspect, because what people say they would do in a given situation is often different from what they actually do in that situation.
Service personnel repeatedly acknowledge that their level of service has almost no relationship to the tips they receive. Women with large breasts get bigger tips. Men get bigger tips than women, whites bigger than blacks.
And an article from an owner of a restaurant who got rid of tipping, increased wages, and found his service improved. I include only for the quote that reinforces my argument that waitstaff are motivated the same as all workers -- I don't support the concept of adding a "service charge" to a bill, or endorse that tipping be eliminated, although I fully support the idea that a business owner be free to adopt a non-tipping paradigm, and that customers be allowed to ask for it, to seek it out, and enjoy it. Free market means not trashing people for wanting something different than you want:
Owner explains why abolish tipping:
Servers are motivated to do a good job in the same ways that everyone else is. Servers want to keep their jobs; servers want to get a raise; servers want to be successful and see themselves as professionals and take pride in their work. In any workplace, everyone is required to perform well, and tips have nothing to do with it. The next time you see your doctor, ask her if she wouldn't do better-quality work if she made minimum wage, with the rest of her income from her patients' tips. I suspect the answer will be a version of “no.”
We are used to tipping. Restaurants love it because they don't have to pay their servers. Servers who are good at extracting tips love it, because they know how to play the game. But there seems to be little evidence that YOUR giving a bigger tip provides YOU any better service, or that the notion of tipping causes waitstaff to provide a better quality of service.
I disagree. I do, in fact, know that my tips have insured good service.
If you don’t like the system, then don’t patronize normal restaurants.