I still think everyone sees a noisy image in the dark if they pay attention. Simply because the retina is underexposed. "Visual snow" usually refers to a more extreme condition where you see it even in good lighting.
Maybe you just don't notice it? It's most noticable in a dark, but not completely dark, room when the eyes got accustomed to the darkness.
To clarify, a similar case: most people are able to see Haidinger's Brush [1], even if they have never noticed it. Why? Because it's not very noticable, so they don't pay attention to it.
