It should be more important. But without organized unions, how many people out there will risk their careers for integrity, especially en masse? How many would see one person quitting on principle and not think, "this is my chance for a promotion"? I'm not familiar with Japan's union culture but I do know people don't switch employment that often and their cultural integrity can drive them to fall into this trap as strongly as it can to leave it. In this case it seems like "honor and integrity" drove the whole group further into the trap. Speaking truth to power is terrifying and potentially self-destructive unless you've got legal protection.
Edit: Apparently Japan actually has a higher percentage of unionized workforce than the USA. I imagine that has shifted quite a lot over the past couple decades with the death of unions in America. But like in America, I imagine Japanese autoworkers at the engineering/management level are not unionized.