Earlier quoted context omitted.
Because we already arbitrarily assign different pronouns to different people, usually based solely on their appearance, and there is no harm in letting people pick which type of gendered (or less gendered, in the binary sense) association they'd rather have.
There's an easier fix for that, instead of having to memorize everyone's "unique" preference (xy/xor/xeps), change the language to avoid the issue. "They" for everyone is the only logical evolution. My native language doesn't have a he/she differentiation..
It's literally identical to the concept of learning someone's name, yet humans largely don't have a problem with that.