In my experience it's a lot, lot harder to create a game that doesn't have gender equality. While we do all play pretend, a lot of people feel uncomfortable writing or reading it. Same way; when I established a setting that is zealously religious; there were far more atheist PC's than NPC's. People will take modern conventions with them into roleplays regardless of setting. Sometimes even without intending to. Be it gender roles, be it belief system (or lack thereof.) The fewer reference points people have, the harder it becomes for them to RP. It's fandom vs. original all over again yo.

Generally, I wouldn't dare to create an RP with gender discrimination in casual and I would think really hard about it whenever I try that in advanced. Is this element worth the hassle? Is my game attractive enough to deal with the loss of players based on the setting's gender equality? Will I feel like explaining people I'm not sexist just for creating a sexist setting? If the answers to this are yes, then let's go. If any of them is no, well, gender equality it is.