I believe the reason is related to the safety of the driver's position in the vehicle rather than the state of being drunk. The driver's seat is the only one gu

I believe the reason is related to the safety of the driver's position in the vehicle rather than the state of being drunk. The driver's seat is the only one guaranteed to be filled each time the car is driven, therefore car companies have a bigger incentive to care about the safety of that seat than any other seat.