Out of all these laziness, I'll tell you why:
Example: If I wanted to be a guy, I'll just tell me people to call me by that. Surgery is too expensive and pointless.
The way i see it:
Do you have a Y chromosome? Great! You're a male!
Do you have only X Chromosomes? Great! You're female!
Male but want me to refer to you as a female? Sure, no big deal, I might mess up once or twice but I'll settle on it soon enough.
Female but want me to refer to you as a male? No problem either, just give me some lee-way in case I accidentally call you a woman, I wont intend it.
Want me to call you Xir/Xim/Xer? Go fuck yourself, I shouldn't have to learn an entire set of "unique" terms just for you, you're just being awkward and you're essentially asking for special treatment and just being a special snowflake. Just because you identify yourself as a certain gender does not mean that I identify you that way. Everyone USES it to refer to biological sex because it's simple, euphemistic, inoffensive. We us it because apparently the term 'sex' makes us all squeamish throughout elementary and middle school so we were just taught to use 'gender' instead of 'sex'. Gender does actually refer to the societal definition of your sex.
I don't really care what people identify themselves as, but other people and the government need some way to identify them, and by sex is the easiest way to do it. You don't need special accommodations just because you feel like a cat trapped in a man's body trapped in a woman's body.
THIS IS WHY AMERICA OWES CHINA TRILLIONS OF DOLLARS OH MY GOD PLEASE STOP