Narrad-
I’m told that parking lights originated because of drive-in theaters. They allowed people to pull in without disturbing the movie by shining their headlights on the screen. Now they are sort of vestigial.
By the way, the above could be completely bogus; I’ve forgotten where I heard it. But it sounds good to me.
-Andrew L
Given this thread’s complaint, you might find this amusing:
I have been taught to turn the parking lights on if I have to stop the car on the side of the road. In Finland, using lights is regulated by law; a motor vehicle in motion must have regular lights on. Parking lights can thus be used to distinguish a car parked on the side of the road from a car in motion. Also, winter nights are pretty dark here, and using parking lights to mark a car stopped on the side of the road greatly decreases the risk of someone ramming into you while you’re getting back into the driver’s seat after answering a call of nature in the nearby bushes.