The point is that they convey information without building trust. Research has shown that face-to-face contact is essential for building trust, because there is a lot of subconscious emotional information conveyed in body language. E-mail and other electronic communication conveys the factual, logical information, but not the emotional information. So if you want representatives to collectively decide things based on what is rational and logical but not be subconsciously influenced by lobbyists or other politickers, cut the emotional channel out of their communications.

It's the same reason that Google makes promotion decisions by a committee located on another continent. You want people to judge based on facts and not impressions, so divorce the objective facts from the subjective impressions.