“For some reason” is a common expression indicating the reason is obvious but not stated.

It’s a big issue. The problem is there are a large amount of elderly people and not enough young people to care for them and keep the economy going.

Population age graphs used to be a triangle. Lots of kids some adults and a few elderly. So there were a lot of people to care for a small number of the elderly and a big group to care for you when you became elderly.

These countries age graphs look like upside down pears. Lots of elderly some working and few children. So more work by the young to care for the elderly.

1.15 in Japan 0.72 in Korea. so yeah.

Both countries have high cost of living and expect women to drop everything and become full time moms and care for their parents and inlaws.

Women for some reason don’t find that appealing and decide to not have kids. Many refuse to get married if there partner wants kids.

Even men often don’t want children as they are expected to work long hours to support the family.