MEN!!!
So if Jerry had listened to Pam, he wouldn't have stopped for the hitchhiker. If Kirk had listened to Pam, they would never have gone to the horror house! Then of course you have he insane Cook, hitchhiker and Leatherface....all men!!!
No small wonder this movie had a final girl....the blokes were all too stupid!
Moral of the story.....women are smarter than men.