Manufacturers are focused on making things in big quantities, but people buy cars one at a time.
The dealer is the interface.
There is no better way to effectively meet customers' demands for distributing manufacturers' (vehicles) than through a franchised dealer, who can satisfy both while preserving the ability to service the product and maintain a stable market. Various types of manufacturer-owned dealership schemes have all been found wanting, when faced with aggressive competition from entrepreneurial dealers with their own capital on the line.
A strong dealer network is the factory's human face in the community, the maker of the market and the factory's reputation, and a vital buffer between the inflexibility of the manufacturing process and abrupt shifts in the market.