Well, for instance, because hearing other languages and translating them is not even the primary use-case for knowing a language. It would take a suite of purpo

Well, for instance, because hearing other languages and translating them is not even the primary use-case for knowing a language. It would take a suite of purpose-built AIs, and the knowledge and ability to use them in-situ, to replace knowing a language. AIs can also teach us to do things they cannot themselves do, for instance you could have a driving-test tutor. It could teach you a lot of things, despite us not having full self-driving AIs.