Have to disagree Mark. In Judo we were always taught to protect our neck and collar against grips. In randori you would often see people with their arms high and close to their head, like a boxers guard. People trying to get grips would throw their arms in fast, as though they were doing straight punches. It's common to see people "blocking" arms in Judo as this means their opponent can't grip. Additionally the "alive" manner of Judo training means a person is getting a good understanding of distance and timing and learn how to stay "arms length" away from someone to stop them gripping.
Additionally, a Judo player learns how to grip to tie up a persons arm. The same ideas can be used to stop someone punching (have played about with this in Judo after class).
Finally you seem to be completely disregarding the Kodokan Goshin Jutsu kata. I'm not a huge fan of this Judo Kata, but it makes an attempt to show how a Judo player can deal with punches, kicks and other attacks:
"Let your food be your medicine, and your medicine be your food"