I have never heard of Kyokushinkai schools fight allowing no glove full contact blows to the face and head. It would seem a little strange to try and learn how to defend yourself at a place where they will make you beat each other up so much!
Either way, punching or not, hand strikes to the head are the most common form of attack in the street.
What is natural is the fact that the brain is the major organ we have, and bouncing that about by striking the head has the best chance of winning you a fight.
Funny how pro boxers wear groin guards but not head guards? I wonder which organ they value most!
