They already know english for the job, so its not like its an extra requirement
Now imagine you're a bush pilot flying around Alaska in a Cesna flying near Anchorage. Imagine being forced to speak German to your fellow American ATCs.
I've never heard of the English rule being ignored anywhere else except perhaps at tiny airports without proper radio discipline. Though I was only a private pilot.
It's not that it has to be in English because it's meant to be a better language. It's because the international community chose it. English is a requirement because lives were lost because of this (think Avianca 52). Foreign pilots have to do a language test to get their license. Even for a PPL. At least here in Europe.
Also the phraseology of radio communication is pretty specific and even a native English speaker wouldn't make heads or tails of it if they have no knowledge of aviation. It isn't really English as such.
It's no coincidence that the French invented the word Chauvinism :) I the multinational company I work for I've never seen a people so angered at having to speak another language than the French.
You're somehow presuming that there is no functional difference between being a native speaker and knowing a language as second or third language.