Well as I suppose the main reason that Westerns don't buy Japanese porn games is precisely because they are censored and Westerns people are just not interested in watching porn or playing porn games when they have censorship and thus the whole porn in fact ceases to be porn for them because just showing only naked tits at most does not encourage anyone who watches porn or plays porn games precisely for the sake of see complete nudity and intimate situations without any censorship.
If they tried to release in the west they’d be trading one form of censorship for another. Sure now they can get rid of the mosaic censorship, but then they’d need to censor or change other aspects of it to get western credit card companies to process the payments. So it’d still be censored in one way in the west and then it’d be an even more heavily censored product to their main consumer base in Japan.
For the vanilla stuff that wouldn’t require censorship in the west they certainly are just leaving money on the table they could easily get but that’s typical of Japan. They do the same thing with anime/manga. They could be making so much more money outside of Japan but they don’t try or just do a poor job.
At the end of the day though it’s for the better. The last thing we need is for them to start doing a great job of monetizing their products in the west to the point where they prioritize a western audience over a Japanese one. Then you could say goodbye to all Japanese incest porn and many other fetishes that wouldn’t be able to be sold in the west.
Also websites like DMM/fanza are region blocked in the west and no longer take western credit cards. I don’t know the exact reason for this but I’d imagine the credit card companies are giving the Japanese a hard time and refusing to process payments because of prominent fetishes like incest or loli. And if I had to guess I’d imagine western credit card companies would still refuse to process payments to the Japanese porn creators, even if they were only trying to release vanilla and/or censored porn in the west so long as they were still creating and releasing things like incest or loli in Japan. So again it comes back to the fact that I don’t think they’d be able to sell porn in the west without completely undermining the Japanese audience by confirming to standards set by western credit card companies.
