>>5019676 In many human attacks cougars go at them from behind, leaping onto the head and shoulders. For children or crouched adults the skull is the most immediately accessible and controllable target.
For smaller prey ( deer fawns, human children, elderly roasties) the head and neck are similar in size, making the skull an easy grip point.
also, human upright posture and cranial size mean a pouncing cat often lands on or near the head.