The next question, of course, is why allow 70-year-olds to drive if their reaction times are no better than a texting teen’s? The answer, of course, is that it isn’t the 70-year-old’s fault that he is 70, and we can’t let anyone lose their license without it being their fault. That would make people feel bad.
Even that question is an evasion though. If reaction times are so important though, why don’t we just administer reaction time tests before issuing or renewing a license?
If we really were security-obsessed risk minimizers we’d have hard criteria to evaluate who qualifies to drive. We can’t have that though because a kind, no-criminal-record, but blind and senile granny somewhere who has never been in an accident
and doesn’t present but nevertheless presents a real threat would lose her license. The responsible congressmen would have to fire someone and the test would be changed iteratively until granny can get behind the wheel again.
But we do want to pay some token of tribute to security. We can do this without threatening the status quo by passing laws that arbitrarily alter already arbitrary laws about how much of what you can consume how long before driving. And we can regulate arbitrary behaviors so that it remains OK to pee into a bottle while driving as long as you’re not also sexting your girlfriend while you’re do it.
We’re not obsessed with risk minimization. We’re obsessed with ensuring that no one should be prevented from driving without it being their own fault.
Edit: Our hypothetical granny presents a real threat.