Except that there aren't just thousands of faces, there are literally billions of different events, personalities and things that you can flip together. And it happens at a very rapid rate. Dreams are just one of those flip strips that you can flip in there. But they also work in terms of advancing the story. Sometimes when I write I can use dreams to have a sort of precognitive effect on the story.
Precognitive dreams are a staple of our supernatural folklore.
You know, the person who dreamed that flight 17 was going to crash and changed his reservation and sure enough, flight 17 crashed. The closest that I can come to a precognitive experience is that I can be in a situation where a really strong feeling of deja vu washes over me. I'm sure that I've been there before. A lot of times I make the association that, at some point, I had a dream about this place and this series of actions, and forgot it with my conscious mind when I awoke. Every now and then dreams can come in handy.