Of course videos disappear for copyright, ToS violations, or when the uploaders remove them. They do not disappear just because nobody watched them.

There’s a whole activity around discovering random 15 year old videos with almost no views. It’s usually some random home video

A friend of mine worked two years in YouTube as a content admin.

Basically being given videos to watch all day, especially coming from the middle east (this was ISIS time so any video from the area had someone watching it as soon as uploaded).

Needless to say there's endless gold no view videos according to him.

It's also interesting that it was no open secret that already in 2018 they were all told that they were essentially training machines to do their job.

I was interested in the same thing and built a search for it

https://ytstalker.mov

They also disappear when the government of Pakistan tells Google to erase them: https://lee-phillips.org/youtube/