That should be a warning to people who think YouTube and Alphabet by extension has any interest in archiving knowledge for the greater good. This is commercial interest and commercial cost cutting.
The fact that they keep it around, for free, over years and years, and at no cost to the user is remarkable to me.
There's a reason why serious archiving of knowledge is left to government institutions.
As much as I don't like Google or Youtube - expectation that they will just store whatever stupid stuff you post forever is unreasonable.
Like I posted some gaming highlights when I was teen and I don't think anyone, but I have ever watched them and I don't even have access to that account anymore. All of that stuff should be deleted.
Even now I occasionally have itch to make a video and I am the only one who watches them, but at least they are good enough for me that I return to watch them.