Can someone care to explain me why the car dealers exist in first place ? Isnt it much more economical for Ford, Toyota etc. to simply start selling cars from t

Can someone care to explain me why the car dealers exist in first place ? Isnt it much more economical for Ford, Toyota etc. to simply start selling cars from their own retail store chains ? It is likely to make cars more cheaper and car companies more profitable. How can any legislation banning it get passed in USA ?