It's partially that for most other media once you have found and cataloged a piece of media/data it's safe. Books don't disappear off my shelves. Even things yo

It's partially that for most other media once you have found and cataloged a piece of media/data it's safe. Books don't disappear off my shelves. Even things you haven't gotten specific copies of generally don't disappear entirely, they may get harder but there's usually a copy /somewhere/. Things on the internet tend to disappear entirely unless they've been included in the few archiving things like archive.org.