> Not making them mandatory means they remain expensive extras, more expensive than if required on all cars. If they were rare they might be more expensive, bu

> Not making them mandatory means they remain expensive extras, more expensive than if required on all cars. If they were rare they might be more expensive, but otherwise it's the same system and will cost about the same amount to incorporate into a vehicle. Making it mandatory doesn't make it any cheaper. (Usually the opposite, in fact. From the POV of those manufacturing the safety systems, there's nothing quite like having the government mandate that people buy your product.) Economy of scale is not guaranteed, or even really all that common once you get past early research and development or one-off custom products and into the realm of mass production. In general commodities become more expensive in response to higher demand, not less. If these systems are something most people actually want and consider worthwhile then they'll already have the benefit of any economy of scale which may apply without the mandate.