One - I will very likely get nightkilled by a vig/Van Helsing anyway, so it would be a waste of a lynch.
Two - I have information know of a certain person who happens to be a werewolf. Now, who's more of a threat? The gang of unknown werewolves that are almost all alive? Or the last vampire, who's been identified and is all but dead?
I have no reason to lie. I'm going to die anyway, but if my mafia can't win, I don't want the other one to either.

So, gentlemen... interested?