Why is it common to hear "women writers" or "woman doctor" but not "man author"? Isn't an adjective required in both cases, thus "female guitarist" and "male accountant"? I am asking about why the noun woman is used instead of the adjective female and why this error seems to be made only in relation to women, not men. This is not a question about the appropriateness of such qualifiers.
You do hear 'male writer' and 'male musicians' only much less often.
This is unfortunately due to most professions being dominated by men leading to women being treated unfairly which will in turn raise a debate. Men are the norm in these professions so there isn't usually a specific detail to discuss (which is why you don't 'hear' it)
You also hear it more often with ethnic minorities for example in the UK 'Black police officers'
This is for many reasons such as there being less black police officers than there should be which raises a debate, and in turn you hear it.
To be honest this is more a question of society than language, but I hope my answer makes sense :)
While the last commenter is right, using "woman" to precede a noun is correct (it is in this usage an "apposite noun")
This column by William Safire goes into the issue with a bit more detail and context
I understood your question just fine--in fact, I was seeking the same answer when I stumbled upon this page.
I think there are two reasons:
No matter if it is good, bad, or indifferent we as people form an image in our head when we hear something. If that "norm" image falls against the grain of what the author is trying to convey then they may proceed the word with a descriptor to offer a different picture. If you take the example of nurse most people automatically think woman. So if an author was talking about a guy, they might say male nurse - so that your mental image is correct(ed).
The second reason is to bring light or celebrate something. If the author wants to highlight a group, minority, anything, he/she may put a descriptor in front to emphasize what the article about. If the author was told to write a monthly article on women authors, then that phrase will come up more.