Some eastern martial arts (such as karate, taekwondo) prohibit straight boxing-style strikes/punches to the head in their sports rules:
A punch that makes strong contact with the opponent's hogu scores 1 point. The punch must be a straight punch with arm extended; jabs, hooks, uppercuts, etc. are permitted but do not score. Punches to the head are not allowed.
Punches to the face, groin, and joint are prohibited but all bare-knuckle and elbow strikes to the body and limbs (with the exception of joints), and kicks (including kicks with the knee) against legs, arms, body, head and face are permitted, as are sweeps.
But why, historically? With respect to these arts, it seems somewhat impractical - these arts have large amount of possible moves, why are such punches prohibited?
My question is absolutely not an attempt to belittle eastern martial arts, but mainly, to ask why. A lack of these strikes influences style and moves - you cannot (in general) afford such a degree of complex kicks in kickboxing (or muai-thai, for example) - you sometimes just don't have time for it - as your opponent is coming close, within knee/fist striking distance.