All dreams happen for a reason as does everything else, but the purpose of dreams well there could be many depending on how you look at it. Like in the film, not everyone has what they want or need for instance the homeless man. The homeless man to me looks like all he wants is just a little company. Of course other things but how it was shown he was lonely. He like that the little girl named Penny would come be with him in the park. But then you start to realize in the video that the girl isn't always there. What it seemed like was that he was almost dreaming that she was there. Then you see at the end of the film that she has to leave and as she is waving goodbye the show where the man was sitting and make it seem as if though she was waving goodbye to nothing. So this could explain one purpose for dreams. Dreams can occur for many people in this homeless man's situation to make take away the reality and sadness of his or hers real life and let them escape to another world (dream) that co-exists. Some people also think that dreams happen to send messages. I don't necessarily believe I honestly don't know if it's true for all I know it could be an old wives tale. So all in all dreams can have many purposes and I strongly believe that.