Why It All Went Wrong

A physicist, a mechanical engineer and a software developer were travelling in a car which broke down. The physicist suggested reviewing the laws of physics to figure out why the car would not work. The mechanical engineer suggested looking under the bonnet. And the software developer proposed that everyone should get out, then get back in again to see if that would reboot the motor. There was a banker in the car too. He said "Give me a fiver each and I'll hire a cab for you three when I've walked back to that town we just passed".
So they did, but they didn't see the banker again. And they are still waiting for the cab.