It all comes down to Japanese peoples' beliefs. They see modding their games as a shameful behavior because they compare it to plagiarism. As ridiculous as it is, they see it as stealing their ideas instead of coming up with your own. In their eyes you should be making your own game from scratch instead of ressurecting theirs.

It's the same reason why Nintendo is so god damn evil. In their eyes they're doing the honorable thing by suing their own customer base.