Most stories consist of the gradual unfolding of information, the asking of questions and answering them. Each set of story ideas and characters have their own inner logic that must be first explained, then followed to a satisfying conclusion.
Given this state of affairs, it is almost irresistable to the writer of sci-fi or fantasy to introduce the notion of prophecy at some level. A cryptic description of the future forms a template for how the story will play out and connects the beginning to the conclusion. Many successful movies and series have used this to great success: The Terminator Movies, Battlestar Galactica, The Matrix, and so on.
The question is, is this a crutch or is it as fundamental a building block as the warp drive, magic spell, the laser canon, and the sword?