Language changes with the times, and when it comes to our conceptions of gender, the times are most certainly changing.
We are opening up to the idea that binary conceptions of gender are unnecessarily rigid and don’t correspond to the self-image of a great many people, and even that people’s sense of their gender may not correspond to their biological sex. In this new world, a bland opposition between “he” and “she” seems increasingly antique, and even insulting, to many.
However, doing something about that is going to be a challenge. We are dealing not with merely giving new names to new things or actions, which is easy, but with using new pronouns, which is very hard.
This is hard because human cognition makes some parts of language more resistant to change than others. Nouns, verbs and adjectives, for example, are like software. It feels natural to add them, subtract them, revise them.
We expect them to change from era to era — of course we now have blogs and twerking when we didn’t 20 years ago; of course young people now call “fierce” what their equivalents long ago called “keen,” “neat,” “wicked,” “rad,” and so on. They are what linguists call open class words.
Pronouns, however, are closed class words. As shorthand for any thing or concept, pronouns are used so often and so unconsciously that they are more like hardware. A new object or practice is one thing — but a new “you” or a new “him” or “her”?
It’s harder to wrap our minds around changing something so cognitively fundamental, just as one does not pop up with new prepositions: You might wish there were a little word to indicate “on as in upside down on a ceiling, rather than on a wall or floor.” But if you made one up it wouldn’t catch on — nouns and verbs are lightbulbs; prepositions are the wiring inside the walls.
Six-thousand years ago, in the ancestor of most of today’s European languages on the Ukranian steppes, while most of the language would have seemed like Hittite to us (because it sort of was!), its speakers were using pronouns that sounded roughly like “me,” “you,” and “we” (not to mention the “tu” familiar from French and Spanish). That’s how hardy pronouns are.
This is why previous attempts to fashion gender-neutral pronouns haven’t caught on (believe it or not, there were once calls for the blend hesh!), and why as clever as today’s “ze” is, its evolution from in-house tradition to society-wide acceptance will be slow at least, and possibly ill-fated. Bias alone will play its part, surely, but even without it, new pronouns require a mental effort analogous to conceiving dimensions beyond the third.