I am guessing drivers also get stiffed more than most poeple just because cars are already pretty expensive, and you know you'lll never see the driver again.
Plus - I hate to say it but there are some shady taxi drivers out there who take the long way on purpose (in a taxi with a meter, not a car service) and if you are from out of town no never really know.
That's why I hate when a cabbie asks me where Im from. I have also "turned in" some cabbies who I know ripped me off. One guy here in my hometown took the far away ebtrabce to our airport - off course I knew better. He made a lie that the city had asked all cabs to use that entrance (pure BS).
I called his company after the ride (I paid the full fare, but no tip so he made no money from me) and told them what he did. The company sent me back my cab fare and told ne they put the driver into a weel-long training session - no income.
I used to catch cabbies in NY because I knew how much a ride from laGuardia to my door cost - and if it was $10 over and regular traffic I owuld look at their wheels - they would be underinflated. So I would tell them "either charge me the right amount or I'm calling your company" and I never had a problem.