Why do we even have gender?

[Autumnwindinthewillows]

Excuse my ignorance - only recently learning about all this.
Given that sex is biologically determined why do we also have a gender? I could possibly understand the point in a language that denotes all nouns male or female but as a purely social construct can't we just do away with it and call ourselves what we want?

I'm reading Ballet Shoes to DS age 9 at the moment, and in chapter 3 Petrova is working on a meccano model, and at the end she goes off to study Engineering. Book first published in 1936 and very much holding up the principle that it's fine for girls to be "girly" if they want to but there's nothing un-girly about being a girl who likes different stuff.

Ah yes Ballet Shoes is great. An actress, a dancer and a scientist. And why not?

Only useful for fitted clothes from what I can see. Although as a lanky teen I used to borrow my dad's old suit jackets.