Furthermore, the win condition for town is the destruction of both vampires and werewolves. The win condition for werewolves is the destruction of humans and vampires. The win condition of vampires is the destruction of werewolves as a priority and...the conversion of humans as a priority.
They could just kill as many humans as possible but the night phases are not reflecting that fact. The drive to keep Dupti alive is based around believing he is telling the truth and not just, y'know, falling on his sword to cause as much distrust and chaos as possible.