True, but I understand it a little. The clinical presentation of DID is very different to the culturally recognized stereotype, so unless a clinician has actually diagnosed a client or had specific professional development about DID many will believe the skepticism about it. Even though the research and understanding about it is growing all the time. Sadly it is just how it is.

It isn't only the DID population that experiences this... a few years ago my daughter was diagnosed with ADHD inattentive type, and after researching it in an effort to understand her better I realized that I have experienced the exact same symptoms all my life. I made an appointment with my doctor to get a referral to a specialist for diagnosis and treatment.
My doctor listened to me then told me that just the previous week she had attended a professional development workshop about undiagnosed ADHD in the adult population. She said if she hadn't been to that she would not have believed me and not given me a referral, but instead she noted that my history and symptoms were consistent with what she had learned the previous week, so was happy to refer me on.
I guess my point is.... they only know what they know, and given the controversial history of MPD/DID I don't blame them for their skepticism.
I don't think it will always be this way. Understandings are changing.