I never quite thought of it that way, but that's why I've always preferred MOTW to mytharc in X-Files and Supernatural both.

(Also, it helps a lot when the heroes are hotties. I don't know why, but it really does. So for Supernatural you know that no matter what the pretty boys will live or there won't be a show, so the ick is fine. Of course, getting attached to anyone else is inadvisable.)