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.
This is a perfectly valid reason to like Ubuntu, and it mirrors my own reason for preferring Mint: familiarity with an OS UI. In my case, Mint Cinnamon is the closest I could find to the Win98 user interface. Back in the old days I also had Ubuntu, but then they switched to the Unity UI and I changed to Lubuntu. That went to the pits a few years ago, so I moved on to Mint. Just like you, I also have a preference for the UI, and I suspect that very many people choose a distro based on their UI preferences. That’s the beauty of Linux: plenty of options for everyone.