Well, storing the text itself takes literally bytes of data. That’s a few orders of magnitude less information to store. WoW allows in-game mail, but limits the size of each mail, how many mails you can have in your box, and automatically expires them. When you multiply each document up by how many each player might make, and how many players you have, the data requirements can become cumbersome.
We also need to consider how inefficient handwriting would be just in terms of size on the page. Printed text is way, way smaller on a page than handwritten text. Especially writing with your whole arm, rather than your fingers.
When I write in the Vive, either in Tilt Brush, or in VR Home, the letters are always pretty big. We’d have to write it then shrink it for it to be usable. Or write on 6 foot tall pages, and have it automatically shrunk.
I think a cool solution would be to write documents offline for use in the game. Have a personal library on orbusvr.com, add to/modify it there and access it in-game. It would be far easier for players to create and organise.
Some form of note-taking while in game would be nice too, but if I was going to write myself some help files for use in-game, I’d rather do the creation offline.