I suspect most who have them off when conditions suggest they would be useful have simply forgotten to turn them on. What used to make me wonder is those who drive with lights on when vision is still fine. Then I bought a car that you can set to automatically turn on the lights, and realised they are set to come on embarrassingly soon ! Worse, go under a bridge and end up flashing the car in front !
Er yes, I was going to say energy isn't free. You are bound to be paying to generate the light. Not much, granted, but something.