Look up Tech Ingredients episode on Radiative Paint.
The fact that people aren’t using something isn’t evidence that it’s not possible or even a great idea, it could be that a practical application didn’t exist before or someone enterprising enough hasn’t come along yet.
When something has been known for millennia and hasn’t been put to a particular use even after decades where it could have been used, that is pretty good evidence that this use isn’t a good idea. Especially when it’s something really simple.
Radiative cooling is great for achieving temperature a bit below ambient at night when you don’t have any modern refrigeration equipment. That’s about all. It’s used in space applications because it’s literally the only option.
The fact that people aren’t using something isn’t evidence that it’s not possible or even a great idea, it could be that a practical application didn’t exist before or someone enterprising enough hasn’t come along yet.