I think a big part of it for RAR specifically is that it’s a proprietary format that would technically require Google to license it, and for the tiny percentage of users that would benefit, they don’t bother.
A seemingly random but relevant example is the Japanese travel card situation with Pixel phones—every pixel on the planet has the necessary hardware to support Japanese travel cards since the pixel 6, however only pixel phones bought in Japan can use the feature (locked by the OS) because it would mean Google would have to pay a per-device cost worldwide.
This is kinda a similar situation I’d bet, they’ve proven they would rather not include the feature than pay for licensing