Then allow people to register their games (they all come with the stupid Proof of Purchase token) and allow owners to download a PDF. I don't see how it matters. Eventually someone will scan the thing and put it on a bit torrent. I see it as a temporary stall at best. It really only does you any good if you have the minis and map pieces.
It's relatively easy to print out high-res scans of map tiles and build your own, if you're so inclined. Minis can be proxied or also printed, if you like PnP minis (there is a whole sub-culture for that sort of thing.) So, if the quest guide was available electronically, there would be precious little to stop people from just making their own copy of the game.
Maybe someone will eventually scan the quest gude and put it up online via some file sharing program (like BitTorrent), but that's hardly a good reason for FFG to do it first. By that logic, movie studios should just put up full-length copies of all their movies for free download as soon as they hit theaters. After all, once a movie hits theaters, it's only a matter of time before people start posting bootlegged digital copies of it online.