It's just that they're, on one hand, too grandiose to admit to themselves and to the world they do have a REAL CHARACTER problem. On the other hand, vulnerable narcissists (all the continuum types tend to migrate to this one when aging) LOVE the victim position; that is not going to the doctors means they can forever COMPLAIN about their "fake" sicknesses to extract huge amounts of narcissistic suply that they do need to survive in the absence of any capacity to genuinely love and see relationships as spaces for healthy reciprocities. They're merely transactions "what is it in it for me?"