How can illusions be a reason to why we can't believe everything we see

Illusions is a reason why we can't believe everything we see because illusions make things appear when it's really not there, and if we believe it's there, it would make us believe in things that aren't real. Illusions distort our perception of reality, meaning that it can change what we "see." A person could see something and see it, while another person can't see what they're seeing. Illusions messes with reality, and could sometimes throw our brains off from the real things we actually see.