"A dream uninterpreted is like a letter unread."
I have been doing a lot of research on this topic for my consciousness class at college. There are so many theories out there as to why. I say why not? Our unconscious is talking to us and helping work out problems and ideas we may miss when our Ego gets involved. There is a lack of control when we sleep. Our defenses are down and our mind is allowed to talk to us about the things we are unwilling to look at (our shadow selves) or is giving us clues as to what is really going on in our lives. Those pesky insecurities, fears and emotions that we deny ourselves of expressing throughout the day need somewhere to go. Many people can lucid dream (be aware of dreaming) and utilize this talent to ask the questions that can decipher what our dreams are trying to tell us. Many can even have fun in dreams and try things they would not or cannot try in waking life, such a flying. Since the laws of gravity or any others for that matter don't apply in dreaming life, it is a whole other world to get to know yourself just a little better...Hope this helped a little. The book Lucid Dreaming by Waggoner is a great read for more information on dreaming. Good luck