I think its because, while many will deny this, theres still a very big stigma with mental illness. Or phobias. Particularly in alot of the older generation (not all! just some! before i get the rage mails!).
Thinking about my dads era. When he was younger in the 50's it was simple, if you had somthign wrong with you, you were essentially institutionalized, possibly lobomatized, or your family kept you in the attic or basement like a dark secret. And people tend to be usually very slow to accept the validity of medical studies vs passed down knowledge.
It sucks, but i think this attitude will be quite prevalent for another 2 or 3 generations at least, because many even in gen y dont believe in mental illness. I used to be one.
all we can do is take care of ourselves the best we can, if you end up having children, be as explanatory to them as possible, show them you understand and care. And maybe they'll be different from us.