We take reasonable, targeted measures to mitigate the risks. What we don't do is embark on a grand social program to eradicate freeway crashes, because such a program would involve banning or heavily restricting cars and we feel cars are too important for that.
The car/cancer/heart-disease analogies are inherently flawed because they're not communicable. If my road rage started a chain reaction across the Interstate causing 45K people to die in a month, I think we'd stop driving until we figured out what was going on.
Every car has to pass a bunch of certifications to be legal to drive on the road. It has to pass a (4-, 2- or 1-)yearly checkup, has to be registered, insurance has to be paid, road tax, etc. Also the driver has to pass a theoretical and a practical exam, has to be of certain age, not be under influence of any of many substances, has to obey a bunch of traffic laws, etc. And we also have check for all that, from police controls, to speed cameras, alco-testers, etc.
Again going back to the cars example: if you did not "just shrug our shoulders at the risks" each car will be equipped with alcohol detecting interlock at the minimum. Of course the society "shrugs the shoulder" as soon as it inconveniences it a bit too much.