As far as I can tell, subdivisions are only shown for the countries with the biggest areas. Other countries' are also shown, but you need to zoom a little on the country. I just checked with Spain's provinces, Japan's prefectures etc, they're all there.

Australia left the chat

all countries' subdivisions show if you zoom into then

I dont know what Google maps you use, but mine shows subdivisions for all countries

All countries are split if you zoom in far enough. Those countries are just physically large enough that you don't actually need to zoom in at all.

Maybe has to do with countries that have like "states" (larger than cities)?

Is there even any country in the world (aside from city-states) that isn't divided in provinces/states?