Why should it default to English for everyone?
Maybe because English is commonly recognised language of international communications? Except SA lobbies English is the only way to keep communication between players from various countries. Splitting lobbies on a smaller regions, e.g. French, German, Italian lobbies, will lead us to increasing overall waiting time. Another possible scenario, when half of the team is speaking on specific language, because this language announced as official language for that lobby (as you suggests), and the rest of players are speaking in English. As result total miscommunication and chaos everywhere.
I think, this is a bad idea. Just learn English a bit. This will help you in a real life.
Status changed to "Declined"