I can have extremely clear dreams with visuals and everything, but when I wake up, I can't visualize any of it. Smells, sounds, feelings and textures, tastes I could remember, but not visual. It just seems that our subconscious is already creating the images, but our conscious that we do control seems to dull it out or mute it entirely for those like myself who straight up can't visualize. Maybe I'm wrong, but that's my best explanation.