Let's see
A driverless taxi can't be drunk
A driverless taxi can't be distracted due sleepdeprivation, trying to earn extra money when they are clearly in no state to be driving
A driverless taxi can't be distracted due to having a bad day, having split up with his/her bf/gf/gik, had an argument with a friend, or dealing with some other financial and emotional issue.
A driverless taxi can't overcharge, either deliberately or accidentally.
A driverless taxi can't get either offended, or unwelcomly interested, when my girlfriend whips her knickers off.
Software can have bugs. But bugs can be fixed. Human qualities are more difficult to alter.