I'm not being snarky, but... how do you know? I mean, if you can't visualize when you are awake, how do you even know what you see/saw when you were dreaming?
I think the range of abilities and experiences around visualization, perceptual memory, and so forth, suggests that seeing and remembering are pretty complicated collections of multiple simultaneous processes that are a little differently expressed in different people, and that are not necessarily perfectly coordinated.
More generally, I think we tend to think of ourselves as singular, but we have pretty good reasons to think that a person isn't actually a singular thing, but is instead a collection of many processes that are only more or less coordinated and cooperating.
The only exception would be the hypnogogic state when I have visual imagery but I'm not entirely present to process it.