I don't want a light on my car when I am away from it. Not a problem where I live but if I am visiting cities that sort of beacon could attract the wrong attention. Most L2 charge stations I've used have a light on the EVSE that shows whether or not the car is charging. I suppose Tesla could modify Supercharger stanchions to have something similar to indicate whether or not a car was done charging. However, Tesla's approach is simply to discourage cars from staying after Supercharging via the idle fee.