In the hot jewish areas like BP and Flatbush, the Taxi drivers, as well as the waiters are used not to get tips.
But, I would always give a tip if I feel the guy did more than needed for his job. If the waiter was super nice, or if the taxi driver waited a few minutes, or had to hear the babies crying, and didn't get nervous / angry etc..
And same is for delivery guys, if he did a standard delivery, then why budge, but if he had to go up steps, shlep big boxes etc.. I think a tip is in place.