Why you MUST speak English (even in Germany) to fly

A Pan Am 727 flight waiting for start clearance in Munich overheard the following:

Lufthansa (in German): "Ground, what is our start clearance time?"

Ground (in English): "If you want an answer you must speak in English."

Lufthansa (in English): "I am a German, flying a German airplane, in Germany. Why must I speak English?"

Unknown voice from another plane (in a beautiful British accent): "Because you lost the bloody war."