Congressmen became Members of Congress. For a time, there were Congresswomen (or, as someone I know called them, Lady Congressmen). But I think that there wouldn't be more than a couple of women in Congress today if they were still referred to as Congresswomen.
Something similar could be said about many job titles that used to end in "man." How much of our mail would be delivered by females if they were referred to as "mail women" --or, worse, "mail ladies"? Now, I've never worked for the Post Office, and probably never will. But I've been referred to as a "mail woman." Sounds like a bit of an oxymoron to me.
But, seriously, I can think of the status of one job that actually improved when its title was de-gendered. I can still remember when hustlers were referred to as "con men," which is short for "confidence man." "Con woman" wouldn't have quite the same ring, and would sound simply strange. So, instead, people who gain your trust so they can hustle and swindle you are called "con artists."
Hmm...Does that mean anyone or anything who leaves or changes gender is an artist?