The actual reason for the PARK light switch is really quite good it's just a case of NO ONE uses it.
Yes, the headlights on our cars are auto off so we don't live them running when we PARK our cars.
PARK lights are designed to be left on when the car is parked on a side street where there is a risk someone may not see your vehicle and collide with it. If the PARK lights are on then the vehicle is much more noticeable. This is good when you are double parked for a short time
Now if there were called CORNERING lamps or anything else...then yes it would be a redundant and totally stupid feature.