and can be found in several kata
Tsuki doesn't mean punch. It means thrust.
If you consider that a closed fist in a kata is likely to represent a grip on something, circular movements found in kata then may not be punches at all, but manipulations of your opponents limbs. i.e. arm locks or similar.
In Heian Godan, the circular movement at the beginning of the kata you're interpreting as a punch, dislocates your opponent's shoulder when applied as an arm lock.
In Tekki Shodan / Naihanchi, the movement positions the opponents arm into a "chicken wing" position up his back, which the subsequent foot stamp and uchi-uke turns into a a similar joint attack to the Godan one. In fact it attacks all 3 arm joints simultaneously.
Ok so why are hook punches commonly used by boxers?
There are 2 aspects to this. The protection that gloves give to the small and delicate bones in the hand, in particular the 4th and 5th metacarpals which are commonly broken.
Boxer's fractures require the use of gloves in sport, and the large gloves make hook punches necessary in order to get round them.
Sporting karate doesn't allow full contact to the head, and so gloves don't have to be so large to protect the hands, and so hook punches are less useful.