For whichever reason, YouTube does not like people having local copies of videos. From YouTube help center article 3037019:
In order to protect the YouTube community, we may prevent signed-out users from accessing YouTube videos when they’re attempting to download material for offline use.
Protect against what? What's wrong with offline use?
They word it as if it is a nefarious thing to do. In fact, they should be glad about it because it saves them bandwidth. If people watch from a local file rather than streaming from YouTube each time, it reduces the server usage at YouTube.
YouTube Premium members are graciously allowed to store videos on their devices for 29 days, after which they are forcibly deleted. The videos are stored in a locked-in location inaccessible from file managers and in a proprietary format that is unplayable by anything besides the YouTube app.
At the end of the video "Google is locking down Android" by Mental Outlaw, he explains that there are legitimate reasons for having local copies of videos, such as an extended period with no Internet access, using Creative Commons media, and preserving history.
YouTube lets people publish original content under a Creative Commons license that explicitly allows reuse, yet does not want people to download the same. They also don't allow videos mentioning any tools for saving videos. (Example: video ID xkyqFiUrhTc.)
My closest guess is that YouTube wants to force people to watch advertisements or pay for YouTube premium.
When YouTube ceases operations, lots of Internet history will be destroyed.
Quote by Karl Voit:
Whenever I tell people that we need to plan for the day when YouTube goes offline, I mostly receive weird reactions. It seems to be the case that people can't think of YouTube being gone. Unfortunately, I'm convinced that most people will face the day when we lose this enormous library of videos.
(No URLs due to possible spam filtering.)
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