To make ICAO happy.
This is hilarious seeing that the FAA pushed ICAO to do something about foreign pilots in FAA airspace not being able to understand American ATC. Just ask our good friend Thomas McSweeney!
Paleeze. This is a case of making the world adapt to the inefficeint manner of using the radio by Americans. It's cheaper and easier to point the finger and make everyone else learn to understand the Americans than spending money on teaching the Americans to atually use R/T and plain language.
Best,
PE