Off-line use. I can refer to paper copies and make notes on them even when I'm not around the computer.
I don't think this is a fair argument for either side. Paperless people spend more time on the computer; people with lots of paper spend more time away from it.
Change control. Many times documents can be changed in the computer and, while it records that there was a change, there's no record anymore of what the document said before the change. The paper copies in my drawer can't be changed and I can pull them out to prove that yes that was what was originally specified.
That's exactly what version control is for. VCS's are better, though, because it's easier to create old versions and it may be harder to forge an old version.
Reliability. I don't have to worry about the contents of my desk drawers and noteboard going *poof* when a system upgrade goes south and it turns out the restore process requires things IT can't afford to do.
Backing up digital data is far easier than paper. On the other hand, spilling coffee on a stack of papers is generally irrecoverable.