Why don't I have visual hallucinations?

I've dabbled in psychedelics over the past few years (20 now and no longer use) and I no longer, no matter the amount ingested, have visual hallucinations - be it hero doses or rec doses. Why is this /b/? And to begin with, the visual hallucinations I had, would only be slight distortions i.e. breathing, wavy, etc. Any thoughts? Combinations of 400mics of acid, which my friends were also tripping heavily off of, with 3.5 grams of cubensis, left me tripping mentally, but no visual distortions whatsoever. 7 grams of Azurescens - nothing but increased mental activity. Is this a common result?