Answer:
Well as to why? It's still a theory or it's still theorized. One is that dreams work hand in hand with sleep to help the brain sort through everything it collects during the waking hours. This is just one upon many others. Our dreams combine verbal, visual and emotional stimuli into a sometimes broken, nonsensical but often entertaining story line is how its been described. But to scientist, it's actually a very complicated topic to explain/talk about.
