Many less people are native English speakers than Spanish or Mandarin speakers... Looking at it from a global majority point of view, in aviation, these two languages should be the only finalists in a race for a single unique aviation language - but that obviously won't happen.
I've flown in France/Quebec with French on frequency, Spain with Spanish on frequency, China with Mandarin on frequency. It's a little spooky, it's difficult to picture the overall situation, but after a few flights one picks up basics like cleared to land/take-off and numbers and besides it's the controller's job to control and the pilot's job to fly.
I'd rather the locals be able to communicate effectively than stumble over their R/T making a mess of the frequency or misunderstanding an instruction.
I have utmost faith and respect for my colleagues on the other side of the radio, and if they make a mistake I have TCAS, and eyes. I probably make more mistakes on a daily basis too... Not a very popular view but I stand by it.
S.