Youtube is a defacto time travel machine when it comes to culture as video. You can watch videos from 2004 and earlier.
It's the only platform that could allow itself to act against copyright laws.
It's part of the cultural heritage of humanity.
Okay, what does that have to do with Google not maintaining history of the videos you watched? You can still bookmark links, download videos for offline use?
The concern is about the account that posted the videos being deleted along with the videos.