You’re right that one might only need English to live in a given country.

But then how much insight has that person into how other people think (they can’t hold a conversation with the vast majority of non english speaking people), or access to local news and studies...

I think many Spanish speaking countries are in the same boat: not speaking the local language means you end up in a foreign friendly bubble with limited access to anything that didn’t get picked up by that english speaking sphere, which will often include the really interesting stuff.