sigh
well, maybe there'd be better incentive to take a risk and try to kill someone if you incorperated a weapon like C4 or something which would make killing people as traitor sneakier. right now the only way you can kill someone is either if your fellow traitors cooperate and help draw people out of the center using weapon lures or something, or distract the people as someone goes for the sniper, or if you attempt to DM like a pro.
its less that they can't/don't do anything and more they don't know how to do it.