Well, how is a doctor who doesn't even know about it supposed to either diagnose it or rule it out? Depression is also something you cannot just reliably diagnose from a blood sample or something, so just going "depression!" as soon as someone starts talking about brain fog and being listless seems unfair. Most Doctors think in categories, they don't want to challenge what they already know and have been practicing for years. So the most important thing now is education, spreading awareness.