Ah, have you missed the point Michel ? In the long run is the cure worse than the disease ? Cost wise. Saves some fuel granted but at what cost $$$.
Heavy Duty Batteries and Starter Motors , coupled with Valve Train stress, etc, Ask Helmet about all the extra wear and tear.
Could be, that like energy used in the life cycle of cars, compared to the energy used to produce and recycle them is lesser. particularly fancy Hybrids ????
I know Manufacturers are under pressure to constantly reduce Emission. Easiest way is to reduce consumption by what ever means.