My GP doctor (who was also DID) told me that DID is far more common than people think. I mean, if you think of just how high the abuse rates are, it does stand to reason that the DD/DID rate is going to be higher also. Many don't like to believe abuse is common (that's a whole other issue).
My first therapist also thought I was "fractured" because I had "Altered states" (which at least in my case, were actually alters).