I have never tried to write an sf story. I have written a this-contemporary-world story. And the reasons and choices to include characters who are, oh, transgendered, black, childfree, physically disabled, or old, say, would be (should be?) different in a world that the author's creating out of his or her head.

What drives me batty is if the social significance of the human differences in a made-up world is exactly the same as in my world or as in some other contemporary or past society. Creating one or more different imaginary societies should give the author the opportunity to show different what-ifs in the social construction of race, gender, etc. And not just the heavy-handed parallels like discriminating against men or white people.