- You don't know how to visualize
If you are wondering this it's likely you think visualization is something other than what it actually is.
Everybody can visualize. Maybe except people who have aphantasia.
Visualization is nothing different than imagining or remembering something. If you can remember how your best friend looks like or imagine a pink unicorn then you can visualize perfectly. You don't see something visually during visualization. Seeing things visually is called
clairvoyance or
psychic sight and it is a "supernatural" ability, it takes time to develop for people who haven't been born with it. Some clairvoyant people sometimes describe visualization as a visual experience, but they are really talking about clairvoyance and not actual visualization.