Human scaling relative to environment

Why is it so difficult to create correct human scales in AI? e.g. petite person would still appear rather large and unrealistic as compared to if you take a picture by your camera of same composition. if you place a person on bed, the person will look large and unable to realistically fit in bed if laying normally. these kind of relative environment to person ratio scaling is odd in AI. standing by a door frame they will look like very tall and large filling most of the frame. yes the subjects look realistic on its own but in overall context.