Porn in China and Korea is illegal and the ones that do exist is heavily underground. I don't think Japanese are as highly sexual as the porn makes them out to be but their society is less conservative and more open I guess so thats why a porn industry was able to develop.
In China, the CCP would go around crushing any attempt to establish a porn industry. Same with Korea I guess.
It's a lot healthier to have a good porn industry because then the men can all jack off to their fantasy girls. Sexual repression can be a bad thing. Like in China, lots of men who are in the countryside with no access to porn and are single and have trouble finding wives and are too poor to go for prostitues, they may end up doing violent stuff and take out their sexual energy by other means.
Porn keeps a single man sane.