I think it has to do with a basic problem in Kenpo and Karate as taught in the USA for the past forty years or so. Tournaments, and the techniques required to be successful in them had taken the front seat ever since these arts have been introduced to the public at large. After the PKA etc. was established, you saw a slight move away from the tournament fighting and a move into kick-boxing skills. Then, when the UFC came in 1993, everyone realized that they had been leaving out a very important part of their studies: GROUND WORK. I think that many didn't realize that their art ever contained effective groundwork originally because they had never been taught it. So, when they realized the need for it, they simply tried to insert BJJ or whatever they could find (Including freestyle wrestling). Those that never left groundwork out of their teaching pretty much kept on doing what they were doing.
Most of the original ground work in the Karate and Kenpo styles had to do with take downs, throws and locks and holds. Not a lot of wrestling. If you went to the ground, you escaped and got back up. Motobu, Funakoshi, Chow etc. all had grappling techniques in their original curriculum. It just didn't really involve very much rolling around on the ground.
If you notice that the Gracies are not nearly as dominant in the MMA stuff as they were ten years ago, you might also notice it's because people have largely learned how to sprawl and get back to their feet if they're taken down. People like Chuck Liddell are prime examples of this. can he grapple? Yes, but he mainly uses it to avoid takedowns and get back to his feet so he can start hitting again.