Except that we do. Singular "they" has been used since Shakespeare. And you likely use singular they in your normal speech. When you don't know anything about a particular person, you ask about their attributes. Who they are and what they like, what their name is.
> Adding additional words to English may be required to deal with people who do not wish to use male or female pronouns, but also do not wish to be called an it
Indeed, and we generally do this by asking what those people want to be called, not by prescribing what they are allowed to be called. Prescriptivist language is both ineffective and rude, much as you trying to tell me what my name is is rude.
That said, even if you're interested in prescriptivist approaches, Merriam-Webster[0], and the OED[1] recognize singular they, as do the APA, NYT, and WaPo style guides.
Singular they, for a nonbinary person who prefers the pronoun, or for a person of unknown gender, is the standard. Stallman is the one causing needless conflict by trying to push a different approach when there already is a standard.
[0]: https://www.merriam-webster.com/words-at-play/singular-nonbi...
[1]: https://public.oed.com/blog/a-brief-history-of-singular-they...