Why We Dream?

I think that the section about dreaming was very interesting and wanted to know more about why we dream. I found an article titled In the Literary Mind, in the Psychology Today, about dreams, why we dream, and theories of dreaming.
http://www.psychologytoday.com/blog/the-literary-mind/200911/why-do-we-dream

Dreaming is defined as a series of thoughts, images, and sensations occurring in a person's mind. But why do we have these different thoughts rolling around in our mind as we sleep. From the article there were 5 different theories of why we dream. (I renamed and used my wording of the theories to save space)

Theory 1: Fight or flight
During our dreams we are actually "rehearing" fight and flight situations, without moving of course. We dream to practice self defense behaviors.
Theory 2: Memory
This theory is about dreaming about the important things that happen in our awake lives. Matt Wilson, a man that studied this theory says "sleep is the process through which we separate the memories worth encoding in long term memory from those worth losing."
Theory 3: Hard Drive
As we dream it allows us to loosen or make new pathways so we can keep important connections, create new connections, or get rid of old connections in the brain.
Theory 4: Psychotherapy
Dreams are a way to think about emotional stuff, without double guessing ourselves or being defensive about it. It's a safe place to deal with emotions.
Theory 5: Nothing To It
Dreams are simply nothing. It is just our conscious that wants to think that there is certain meaning behind what we dream about.

Reading and analyzing these different theories, there was not really one theory that stood out to me and answered the question of why we dream. I think depending on the situation and what the dream was about, a different theory could be used. I am usually am never the one to be "in the middle" of a decision or unable to pick sides, but dealing with why we dream, I have to go against that. With what I read in our book and with this article and others I researched, I would have to say that all of these theories at some time and point could be true. Some do seem a little strange but as your read the article, they are all supported by labs and people with credibility. As much as I believe these theories are truly reasons why we dream, are there more? I find it hard, that these five simple theories of why we have thoughts, images, and sensations going around our minds while we sleep are the only reasons. Are there other reasons? If so, are they more reliable then theses sources? Should more theories be added to this list?