There's a lot of effort going into this, actually. My father was a nurse for 30 years and in his nursing school graduation photo, and his retirement photo with his colleagues, he was still the only male. It's possible men view these fields as female dominated and resist applying. It also raises the awkward question of how men are treated in female dominated fields. Would a man be treated better in a female dominated field, than a female in a male dominated field, or the same? I've not seen research on this, unless someone knows of any?

I would go ahead and say because men are just not interested in those careers as much as women. That's the whole point. And that is fine.