I read about why HIV was more common in gay men at the beginning and it just has to do with the transmission of the virus being more likely during anal sex, basically, just due to the tissues and mechanics involved. That surprises me that women are not included because if PIV sex was already less likely to transmit HIV than anal, you would think it would be easy to test for when studying a drug like this?
Looks like it's not approved for women because it hasn't been proven to prevent transmission through vaginal sex - but of course, that's because the clinical trials didn't even include women.