When you own a lot of books physical storage becomes an issue. I had to stop buying physical books because I have nowhere to put them.

Ah, that’s a very valid use case. I sadly don’t read as much as I’d like to (I only have a couple dozen books to my name, though I’m in my mid 20s.) I can see storage becoming an issue though if one owns hundreds, if not thousands, of books. Not a bad problem to have I suppose!