A couple of questions:
Why no punching to the head in tournaments? Knees & kicks can do much more damage. Is it to protect hands? Is it considered easier to defend a kick/knee?
Where & when does kick boxing come on TV? A quick search says Spike, but I only seem to catch MMA fights.
The aim of the Kyokushin training is "real fighting". This is simulated as much as possible in the tournaments and is the reason why they are bare knuckle, full contact and based on knock out or tKo, vs. being based on a point system like the rest of the Karate community.
That said, if it were to allow face punching under those conditions then the matches would never last, cuts would be rampant, blood in general would just simply be everywhere, and it would cause overall public interest to virtually not even exist, let alone would these tournaments find it easy to be sanctioned/allowed anywhere.
By eliminating face punching, the hardcore nature of fighting is maintained while also preserving overall quality of the match/tournament.
Believe it or not, even that still doesn't satisfy a few states in the U.S., and other places abroad. There are still long tedious processes in place in states like NY and MI for Kyokushin matches to find a venue. NY has gotten much better in leaps and bounds in the past few years though.
But when you take that into account, you realize very quickly that allowing face punching would be a quick one way ticket down a slippery slope to Bannedville for Kyokushin karate in virtually any developed nation.
*Kyokushin has a handful of offshoot styles formed by former high-ranking Kyokushin guys who split after Sosai Mas Oyama's passing for various reasons. They are all full contact, just like Kyokushin, but with slight variations in their approach to training/tournaments. They are still all "knockdown" Karate. One in particular, Daido Juku(also simply known as Kudo)
does allow face punching in their tournaments, amongst other things. Kudo is simply Kyokushin with face punching, grabbing, and throws allowed. The difference is they use face shields. Although the shields appear to be very protective, upon close examination it's quickly realized that the protection is mostly for the eyes/nose/teeth areas. The chin and entire jaw line remain exposed. This is evident in the number of punch KO's in their tournaments. Many refer to Kudo as simply MMA in a Gi(short for Dogi, Japanese word for Karate uniform). Here is a short clip of the typical Kudo tournament, and an exhibit of what Kyokushin is like with a different rule set.