If you were to solely take into account job market size then China alone would dwarf the entire list and require a massive team to maintain on its own for what I hope should be obvious reasons.

And this ignores that the job market size isn't related to the complexity of integration. If you're doing business in China your data retention and storage is going to be massively different than Europe which is different than the US which is different than Japan which is different than Indonesia. These will require some form of backend customization and integration with the common UI framework they use for their site design. You need QA teams, you need lawyers, you need managers and live ops engineers and specialists and researchers to drive user retention and businessmen to reach out to companies.

Have you ever worked in a global team environment? Or perhaps talked to your coworkers working on similar products in other countries?