If we think about it… in most cases it all converges to, and probably all depends upon the punch / kick in a scene, just after it.

Chion had made a valid point when he stated that such a short-in-time sound is easier to be marked, on our own conscience,  on shape and timber. And, in some cases, if we cut sound, we realize there wasn’t even a real physical contact. It goes back to the sense that hearing is faster than our eyes. This being said, probably (apart from the habituation) explains why do punches, kicks need to sound like that, in a way that has nothing to do with reality.

Strikes of this type are the strongest synchronization points where sound meets image, in a  most accentuated way; its emergency is governed by Gestalt principles.

Because the moments after and before (nowadays, depending on the film genre, everyday getting more whooshes and sounds alike to provide the scene with predefined rhythm and movement) there is not a rule or a principle to obey in terms of sync with sound and picture, allowing the stretching and / or contraction of time [1]. Not exclusive to strikes, though…

How to: http://filmsound.org/studiosound/pp_fightclub.html

References:

CHION, Michel, Audiovision