It's interesting that this is a problem. I would guess that it's mostly to do with the problem of interaction and eye strain associated with on-screen information.

I can interact with most things on a monitor, but math is one of the things that I still need paper or a whiteboard for.

I have friends that can't stare at a screen for 16 hours a day like I can, and I assume that's the other problem.

Either way, I hate it when somebody comes by and has my email to them printed out and ready to "discuss" and the discussion is just yes or no.