It isn't surprising if you understand how Japanese work culture works. In a nutshell it's all about appearances. You're expected to work very long hours and take part in after-hours work activities e.g. going drinking with potential customers. But the actual efficiency of your work doesn't matter, only that you appear to be working and 'sacrificing' yourself for the company. So what people do is they do real work 40 hours a week, then pretend to work - making themselves look busy - an extra 30 hours per week, unpaid. In the end on paper it says they worked 70 hours but those hours were incredibly inefficient. The person who does this gets the promotion because they fulfilled what the culture expected of them. You tack-on the extra work activities after work, and you end up with a burned out population that has no time for leisure or raising children. Most workers don't even take their yearly vacation time because the culture considers that it reflects poorly on them; they would get snide, under-handed comments from their boss and coworkers. They even have a word for killing yourself through work (karoshi), any culture that feels the need to create a word for that is in trouble.
The issue is that Japan is very conservative, they don't like changing anything. This can be good sometimes, but in other instances like this one it's not good. They have this obviously insane, toxic and counter-productive work culture, but they just... don't change it.