Punching Methods - Why?

All

I have used the Phrase "Karate Punching" but this goes along with any style that give a "Punch from the Hip"

I would love to know why doe we practice "Karate Punching" when we go into Kumite (Sparring or Fighting) (especially when practicing Knock Down Karate and K-1 etc), do we not punch like this. I find it a waste of time learning to "punch" like this then when you have to punch you all instinctively punch like a Boxer!

Karate Punching

http://www.youtube.com/watch?v=fjwxff6c7sM

Boxer Punching

http://www.youtube.com/watch?v=aDZumdvlGxU

I can only see lack of protection for the Head, punching like this

What are your opinions. Which do you teach/practice and why?
_________________________
A man is but the product of his thoughts what he thinks, he becomes.

Ken