Eli5: Why do you use “they” for non-gendered speech instead of “it”?

Question

I’m not a native speaker, but as far as I understood, for singular objects and animals “it” was used. Why use “they” for individual people then?

In: 1400

Answer 1

In some languages, it is a fairly standard pronoun.

In Finnish, the pronoun “it” is not uncommon.

However, in English we have been taught that “it” is for animals and inanimate objects, so to some it sounds rude, and “they” is someone’s preference, so to be respected.