Yes, people do tip more for good service, but they don't tip that much more. Literally, the weather outside has as much of an influence on tipping as does the level of service.
We tend to think of America as a place where the voluntary tip is king. Today, that's not necessarily the case.
Extroverts are outgoing, dominating, social people -- and tipping is an incentive for the server to pay you attention. Neurotics are prone to guilt and generalized anxiety -- maybe they tip more because of guilt over status differences between themselves and the server.