Maybe that teaching influence it as well, particularly after human reach industrialization that discourage people to have families because of financial burden and women entering job market.
East Asian region really dont play much important on religion, mostly they are atheist or worshipping their ancestor or Goddess (many Gods, they can pick one that they feel close to),Buddism is also a factor on that belief since ideologically the religion teach their followers that God is not important for human life since human life is based on Karma and that Karma system that is highly important for Buddish.
Non religious people also can play with prostitute much easily, releasing their sex desire without the fear of committing big sins. Although Christian Protestant belief who say as long as you believe in Jesus you will go to heaven also make this sex before married become easy to do.
Religious people like Muslim is forced by the religion not to have sex before married, it makes them marry to taste sex legally. Once you get marry legally, it is easier to push the couple to have kids since marriage will make stronger bond between men and women. Also if men intend to marry a women, the men become selective, the same thing also happen to women, they become selective as well. The match between two couple with has marriage intention also make them get stronger emotional bond, this will also make couple want to have kids.
Marriage also give assurance to both men and women to have kids, for men they are getting confident that with the present of the wife, the kid will get mother who love them, while for women, marriage give them financial assurance to raise kids as well since the man ( husband ) is a person that has committed to live with her and usually women select men with capable financial capability and the ability to lead a family as husband ( beside other preferable factors based on women mind )