Stupid Ending

Because Lilly made him choose between her and his car.

Oh but did he REALLY? I'm not so sure about that. What I understood was he promised to spend a lot less time with his car, but not that he stopped all together. Otherwise, what would he do for a living? Don't forget, he was a pizza delivery guy before becoming a cab driver...

He did not stop being a "cap" driver in the end. He only promised his girlfriend to be a better boyfriend and to be a great father.