Japan is known as a highly developed country in the entertainment industry, and games are no exception.
Sony and Nintendo can be said to be open systems.
Many Japanese studios are located near the headquarters of Sony and Nintendo.
Speaking of getting developer support, Sony is notoriously good at giving them third-party support.
The cooperative relationship between Sony as well as Nintendo and game publishers has been around for decades.
Furthermore, consoles from Sony and Nintendo are very popular in Japan.
And most of all, game developers are too familiar with products on the Switch and PS4 platforms.
Not to mention the Japanese often aim to optimize space in design.
In short, game development companies in Japan often tend to cooperate with their long-standing partners Sony and Nintendo rather than pushing to develop a game on a platform that has never been popular.