A driver won't just chose profitable over unprofitable, but also more profitable over less profitable, and this ends up hurting some passengers on less profitable / less desirable routes.
If you wanted a cab to Brooklyn from Manhattan 20+ years ago, you had to get in the back of the car before telling the driver where you wanted to go. Otherwise the driver would just drive off without you. The ride was definitely profitable, but they knew they'd pick up another Manhattan ride on the next block and so on - a more profitable option that to risk not having a fare back from Brooklyn. Many drivers wised up and wouldn't let you into the cab until you told them where you were going. It was a major PitA.
If you wanted a cab to Brooklyn from Manhattan 20+ years ago, you had to get in the back of the car before telling the driver where you wanted to go. Otherwise the driver would just drive off without you. The ride was definitely profitable, but they knew they'd pick up another Manhattan ride on the next block and so on - a more profitable option that to risk not having a fare back from Brooklyn. Many drivers wised up and wouldn't let you into the cab until you told them where you were going. It was a major PitA.