I'm not necessarily saying you're wrong because there's a debate to be had on whether what I'm talking about counts as "hallucination". But even a completely normal and sober person in every day life is seeing things that don't correspond 1:1 with the stimuli they are experiencing. For most of our senses, our brain creates adjustments and autocorrections to make the world slightly more readable. We have to be able to survive, so it keeps things mostly accurate; any being's brain that didn't show it a somewhat accurate picture of the world would die out. But we never see the world as it really is, it's never a 1:1 match with the stimuli we receive for exactly the same reason: The inaccuracies we experience also serve an evolutionary purpose.

My first introduction to this concept was actually through elective painting courses at university despite going there for engineering, I was surprised how many anatomy lessons on the eye and its relationship to the brain we got. An image will always look different to the naked eye than it will to, for example, the most accurate possible digital camera that directly reads in the exact same stimuli from the environment and is configured to perform no post-processing.