We’re talking about Android, unrar doesn’t have anything to do with this really.
RAR is and will continue to be a proprietary format with an owner who can seek royalties.
It’s like saying Google should stop licensing MPEG because ffmpeg exists—it simply doesn’t work like that
Ah fair play, I didn’t realise unrar was from the same guy, cheers for the extra context.
So I guess we go back to what else it could be:
There’s probably other reasons I’ve not thought of, but just a couple of the above are enough to explain it IMO