Rainwater harvesting by car

When rain falls on the car, why not harvest it? If the car can filter and store the rain water, then it can be used for multiple purposes like along with normal wiper operation, automatic cleaning of other glass parts like head lights etc. Also, the stored water can be let out through dedicated outlets on top and side of the car which can be used to clean/wash the car, thus saving precious water in the house. The water stored can also be used similar to a wash basin for the car passengers (after eating a pizza from the car, for example) :-) So when is a car manufacturer going to take notice of this idea?