Then again I guess YouTube makes money from ads on these videos being up, so that does explain the sphinx-like impassivity.
But the thing is: copyright law specifies that mechanical royalties are compulsory. Artists don't get to stop you from covering songs, as long as your distributor pays the legal n% to their distributor. But even if you pay LANDR or whoever to administer those royalties, so you can release your cover to Spotify and whatever, YouTube will still smack your channel for uploading the cover. At worst, content strike, at best you still lose all monetization.
As it turns out, "sync licenses" (the right to pair music with visual media) are not compulsory and that's what YouTube primarily cares about. Even if it's just a "video" of your album art with the music playing, you can still be arbitrarily penalized on the most popular platform for music discovery, because it's technically video and record labels can do whatever they want within the opaque framework YouTube has created.
General principle of the internet seems to be people can host what they like till someone who has legal ownership of it tells them to take it down at that point they're expected to take it down and keep it off their service unless added by the owner.
That's what google is sticking to because frankly any other method would be a nightmare.
The old tv episodes might have muddy/unclear ownership and so things continue to coast along until someone exercises their right of ownership.