Good question. (Not your favorite librarian.)
I remember preserving some documents on the original floppy discs, which were floppy. Not only have I lost the discs, if I did have them it would not be easy to find a way to read them.
And the 3.5 "floppies", which were rigid, are going the way of the crank start, too. An option, but not for long.
I've got old hard drives I can't read.
And I still have a few reams of paper files of letters, articles and memo's I've written. I suspect those will last longer, or have lasted longer, than the electronic copies. Or at least access to the electronic copies.
Arf