zlacker

It isn't wrong, but we aren't talking about the model somehow magically transcending the data it's seen. We're talking about making sure the data it sees is representative, so the results it outputs are as well.

Given that male nurses exist (and though less common, certainly aren't rare), why has the model apparently seen so few?

There actually is a fairly simple explanation: because the images it has seen labelled "nurse" are more likely from stock photography sites rather than photos of actual nurses, and stock photography is often stereotypical rather than typical.