of a most complex matter: the infinite assortment of peoples' reasons for driving, the time aspects and especially; the way in which skill reduces the probability of error. It isn't just about physics - and even if it were, some like to sky-dive and some are fearful of own shadow. Few live a life dedicated 24/7 to maximizing 'safety' or even longevity! (Well.. there Are Economists, of course ;-)
If you don't drive, you cannot be aware of the very great differences in skill and especially: of discrimination. Part of that last is, as others in the thread have expanded - reserving higher speeds for areas appropriate to them. (I believe motorcycles inculcate this discrimination much faster and better than cars, which give especially the incompetents, a quite false sense of security).
Above all - higher speed demands higher *Attention. IMhO, it is inattention at the root of most (non-drugged) so-called 'accidents'. This even before general incompetence. And sloth.
* anecdote: it's said that when Juan Manuel Fangio, a legendary road racer - rode with ordinary drivers, he would often exclaim, Attention !! .. as he noticed a situation developing, before the average driver would. Maybe annoying - but at least he didn't die at hands of a distracted incompetent either.
At any rate - the topic is too large for such a digital slogan. But I'll give you: yes, there are (too) many who drive faster than their earned level of competence. YAN manifestation of creeping dumbth. Dumbth: #1 killer by all 'means'.
Ashton
PS - Speed DOES NOT kill: G-force of deceleration + local (penetrating) force/unit-area into bodies - kills. Some situations on road are best evaded by acceleration than braking, skidding while braking .. yada yada. It's an art form, living under physics Rulez.