It seems like we only started doing it because someone decided "female" was suddenly a word to be avoided regardless of context, for reasons that elude me. "Male" seems to still be fine, fortunately.
I've probably heard Male Nurse vs. Nurse (who's a male) about 50/50 at this point. As the world learns that gender is not a prerequisite for nearly every job title, then these gender qualifiers will probably diminish.
Language is a slippery slope though. I don't think it should be read into too much.
[EDIT] word "noun" where I intended "adjective" fixed.
- man housekeeper
- man secretary
- man escort
Wow, these all sound absolutely awful. How did the female, err, woman version become such an accepted construct?
It's much worse! https://en.wikipedia.org/wiki/Murse
I'm told it's not that way in the military, but it definitely is in many subcultures. Working with poor urban kids, I saw this all the time. "Don't listen to that female", etc. It's not something progressives just came up with--it's very much used as a derogatory term by a lot of people in the US.
(There is also the probably-related progressive concept of "people-first language"--you're not an "addict", you're a person who's addicted. Funnily enough, my first introduction to this was Cryptonomicon, and only in the past couple years have I heard it pushed by progressives.)