Why are so many movies so predictable? (spoilers)

I saw Hide & Seek on the television last night and, to be fair, I quite enjoyed it. I didn't know anything about it and that certainly helped. The acting was top notch and I thought the film had a nice creepy atmosphere. But the plot was very predictable.

Spoilers ahead. I do usually like films of this genre and thought I'd seen most, so it was nice to find one that had slipped under the radar. For a while, I was wondering if it would turn out to be some sort of ghost movie, but about a quarter or a third of the way into the film it was pretty clear that De Niro's character was a "DID" case. And it was equally clear that the cop would end up getting murdered, the spooky estate agent was just a red herring and Famke Jansen would end up killing De Niro. The film stuck to the usual formula very rigidly, and it disappointed me in this respect. The best films are those that show a bit more imagination, but so many of them don't.

So, while it was a good film in my opinion, I wish more writers and directors would be a little more adventurous with the way they develop plots, particularly in the horror and thriller genres.