So on YC there were a good half dozen pieces of ripped tzitzis on the floor when I went down. What do we do with these pieces? No one wraps them up for burying them, so the normal solution is to “use them as a bookmark” in a sefer. But if you’ve ever used a sefer with a pieces of tzitzis in it, you know how annoying it is. So any sefer that has one goes on the top shelf. If you need to use that sefer ever again you’ll buy a new one.
As time goes on, you find more and more tzitzis pieces. Now you know why we need so many seforim. Its either that or stop learning.