Wouldn't it make sense to study both normal and pathological personality together from the same framework?

While regular personality psychology is all about stuff like Big 5, HEXACO, or temperament, character, or in past Freudian ideas like ego, superego, id, etc... the science of personality disorders seems to come from a completely different framework. It typically just lists symptoms and classifies disorders without relating any of that to any general theories of personality.

I mean, in medicine, if you know that normal blood pressure is around 120/80, it's easy to see that 160/110 is hypertension. You compare abnormal to normal. You look at both from the same framework.

Why is this not the case in psychology?

The answer that psychology deals with normal psyche and psychiatry with mental illness is not satisfactory to me. I think that psychology as a science that studies mind should be able to understand both normal and pathological functioning of mind. From scientific point of view the fact that psychologists don't prescribe drugs is irrelevant. They still treat mental illnesses as therapists. And so I think it would be better if there was a more integrating personality theory that covers both normal and abnormal personality, and explains abnormalities in terms of deviations from normal.