Also, further to your point that you're not allowed to know about what's on other players sheets, that makes perfect sense. In the GRAND, PERFECT UTOPIA THE FRIEND COMPUTER LETS US LIVE IN, ALL HAIL FRIEND COMPUTER, secret societies and mutants are forbidden. And, of course, you're all mutants and members of secret societies.
Further, as the rulebook says, this is not "you and me against the world", this is "you AGAINST me and if the world gets in the way, we'll tell it to fuck off until we start fighting". One of the main points of the game is to dick over your players. In fact, if you get to the briefing without one person dying, you are either doing it wrong, or are taking your sweet time about it. So, knowing specific details about the other players means you'd know what to do to dick them over. It'd be sorta like being able to see another player's hand in poker, all the time.