People used to leave their cars running while shopping , too !
Or leave the keys in the ignition !
I don't remember cars being left running but cars were not as dependable then as they are now. They wouldn't start or they would flood out and you would have to wait to start them. I remember we always left our keys in the ignition and I don't remember a car even being stolen. I remember seeing someone take their keys out and put them in his pocket and I thought it a very strange thing to do.