To add to what Striker said, you will find that a lot of players are more interested in killing you or getting you to race if you are lucky.
I personally tend to just drive around the city, hang around restaurants and places of interest in an RP fashion, ferry players about with my car, and I occasionally kill in self defense or revenge. I'd like to see more people acting in a more realistic way in the city for the good of RP, but it rarely happens.
That isn't to say someone couldn't start their own RP server or try to set a standard for roleplay.