NicceaActually this is a good point, the mafia would have a harder time hiding.
The other side of the coin is the mafia usually hide behind the townies. It is easier for them, especially the godfather to do so, because the detective is blind to him. One "with it" mayor can find the all the mafia quickly during a role collection or at least have a narrow list of suspects.
That's what was wrong with the game where everyone got a role...