It's true what you say about volatility. It's not just the internet, it's everything digital, even offline storage.

A few months ago I was about to sell/give away a bunch of old childrens books that I had, my reasoning being that I will never want to read them again, and even if did want to for whatever reason, I could always find ebook versions of them.

Ultimately I decided to keep the books -- what if, sometime in the future, I wanted to share these books with my (potential) children? Would all of these books have been preserved in digital form? Would I rather be giving my children a physical copy that I owned and read personally, or emailing a PDF? Physical media holds real value.