Or it's possibly a part of their culture to warn others to avoid bad investments
We all of us do that, it's not just them.
the developers to not put out products that merit that kind of feedback
You're seriously suggesting that games should be released in a condition that they'll never, ever, receive a negative review? Have you SEEN steam reviews and the sort of nonsense reasons that sometimes get left?
The problem is not that they're leaving negative reviews, it's that they're not leaving any positive ones to counter that. In that case, why would any game developer wish to court the tiny Japanese market if they're going to tank the game's review scores?