Because cars are not, in and of themselves, inherently deadly any more than a train or a boat or a plane are inherently deadly. The fatality component of a vehicle largely rests on operators and those who are around vehicles. If a pedestrian on their phone steps off the sidewalk onto the road and gets struck by a vehicle is that the vehicle's or even the driver's fault? Of course not, just like a pedestrian is not at fault if they are crossing the street properly and a driver ignores the crosswalk or red lights. This issue cannot be solved by simply putting more sensors in a car, drivers and pedestrians need to take responsibility for their actions and understand exactly what they are doing when they cross each-other's path.