Most likely answer is that they do it for the same reason as Facebook not sorting their feed by date: they want users to fully rely on their algorithm. My completely uneducated guess is that they want to feed their users older videos where they don’t pay out as much to their creators as they do for new videos.

Youtube wants to own what you watch. Thats why they pivot so hard from showing you the subscriber list first and want to bank on their own algorithm to choose what you see.

Once they do, they have a captured audience of millions they get to choose what you think, buy, see ads for and become addicted too.