Blacks rarely tip.
Friend of mine is a waitress. Blacks tip $2 on average per head, regardless of the cost of the meal. They are also prone to complain about something about the meal or service (b.s.) to justify not leaving a tip.
Cabbies combine that with the risk of getting robbed... and drive on.
Denny’s was sued and settled a ‘discrimination suit’ over this. Waitresses making $2 an hour didn’t want to work for nothing. Racists!
When I am in Chicago I stop and get a bulk bag of Godiva chocolates. I give two or three of these with my tip. After that they will remember you and go out of their way to help you. One of the things I hear after this is “Let me get the door for you candy man”. It is a cheap and easy way to show appreciation for good service and to get better service latter on.