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

I am a teacher of English as a foreign language and after YEARS of trying to get people to get their grammar correctly, I can’t even begin to describe how much this irks me. If they want a neutral pronoun that doesn’t also mean “table”, I’m all for Te, or Ti or Ir, or whatever they want. But “they are” for a singular is… Urgh.