I’d like to think that while awake, we(our brains & sensory organs) notice / observe / perceive more than our thoughts can focus on at a time (of-course this is the whole basis for subliminal messages), so in reality, it only seems we saw those singular things we could focus on even though our brains took note of more and had them stashed away. You get dreams? have you at some point seen people you don't know in your dreams, how's that possible? It posses two possibilities, Those things, people or ideas we observed in our dreams are partly(or hugely) a manifestation of our "stashed" experiences during our "wake" moments - this would suggest that indeed nothing seen in dreams are outside of what is possible in reality when "illogical" experiences are stripped away from them(the dreams) In some dreams we experience things that we can't seem to describe once awake: you've probably heard that you can only think of something you already know; If I said you should imagine a burning match-box and you didn't know what a match-box was in the first place, it'd be an impossible task. again, is our "mental" / "conscious" self in-charge during our dream state? I'd like to think not, but whatever is in-charge has access to all our experiences up to that point. Heck! it could have access to a higher level of consciousness / experience... To conclude I’d also like to think that in our dream state we can go beyond what our conscious mind knows, only catch most of the times is that when we wake, we can’t describe what we saw because the consciousness(using the word "consciousness" loosely in this paragraph, "thought" could be a better word here) from our present reality is now in-charge. PS: what if those that can't remember what they dream have totally abstract(by abstract here, I mean of things totally inexperienced or inexistent in our reality) dreams each time they sleep which their conscious mind can not fathom or piece-together with experiences from our limited reality. Saying this while not disputing that its possible not to get dreams at all Cheers mate 😊