This is a problem in many developed nations, the general reasoning boils down to 1. Cost of living and child care 2. Work, stress and lack of free time 3. Little to no support from society and community. The reason this is affecting Korea, Japan and China so much is that there aren't many immigrants to offset the lack of new children being born. There is a lot of wealth being generated but most of it goes to people w…
Packing even more people into these nations, with the added political tensions of making them foreign immigrants vs domestic growth of native population would exacerbate the original problem with added downside.
Look at the density, cost of living and other factors that flow from "too many people in one place". The natural counter trend must run its course.