Drivers not only need to concentrate on physical driving, but constantly make calculations that lead to critical decisions on the road.
Good depth perception (for accurate steering judgment as in approaching the apex of a corner) and the ability to integrate information from the central and peripheral visual field (when amongst other vehicles) are some of the important visual performance skills used.
Driving requires more than just eye/hand coordination. Visual reaction time, peripheral awareness, and the ability to judge distance and make effective decisions while driving are all imperative skills which require training.
For everyday driving and in a dynamic driving profession, a driver who is visually fit is able also to be focused and to concentrate better, and for longer periods of time.