yes, because google has a habit of removing content from youtube, even educational content. (they made a policy to remove infosec content last year which they deem dangerous)
Youtubes copyright enforcement can hit videos at random, parodies like DBZA have been lucky enough to reappear after a few months. Other channels discussing movies or really anything else that might contain a few seconds of copyrighted music in the background can suffer random bouts of silence. So there are good reasons someone might feel the need to keep a personal backup outside of youtube.
moreover, some youtubers remove their stuff