Why is the use of gender-neutral language becoming more commonplace?

As society changes, language reflects what is changing. For example, the fact that many occupations used to end in -man (mailman, workman, etc) reflected the reality that men had jobs outside the home, while women were expected to be housewives, focused on raising the kids and keeping the house clean. Similarly, the English language used the pronouns "he" and "his" and the noun "man" to represent society in general, even if females were included in the group: "Everyone must bring his book to class." This reflected that men were dominant in the culture; in fact, under the common law, the husband or father was considered a legal "person" while the wife or daughter was considered his property. And when a woman did enter an occupation that society considered unusual, the language noted it: "doctor" was the norm, but if the doctor was female, it was a "woman doctor." (In older English, an -ess suffix showed that the person was a woman: stewardess or editress, to cite two examples.)

And then it all changed, beginning with the second wave of feminism and the women's movement of the 1960s-1970s. Women wanted to know why traditional gender roles were enshrined in language, and they began to ask for more neutral language. As more young women went to college and entered medical school, dental school, even engineering school, seeing a female in one of those roles no longer was so odd, and gradually the idea of a "woman doctor" or a "woman scientist" was replaced by just a "doctor" or a "scientist," whether male or female. The pronoun problem has remained a problem, however-- "he or she" is cumbersome to say, and "their" is ungrammatical, although some people do use it these days. But more important, Words about occupations that used to be gendered and reserved for men are now expressed in a more neutral way-- "letter carrier" or "postal worker" rather than "mail man," or "flight attendant" rather than "stewardess." And men who go into the nursing profession are much more common now, so we don't hear about a "male nurse"-- it's just a nurse, whether male or female.