For some, I think owning a sheet of banknotes is cool. But what do you do with it? Mount it in a picture frame and put it on the wall of just keep it in the tube?
After a while, it just takes up space in some closet and nobody wants it, so they took it to the bank and got real money.
I suppose they could have gotten out their scissors and cut them up or made error notes but going to the bank, seems like the best answer.