Nor should they in this game. That's another point I made: too many groups make for a broken game of mafia. See last game: If you have three groups (town, wolves, crost), the loser is whoever fails to team up. Period. Its dumb.Combining them wouldn't really make sense, they don't work together.
The neutrals in this game shouldn't know each other. You may say it makes no sense that the League don't know each other, but it makes no sense that the cop doesnt know who the doctor is in mafia too: that's the whole point of the game.