Well, clearly to avoid accidents as stated above. Dont really understand your way of reasoning. Whether you speak 35% or 75% native language, the second language used and in this case english should be at a minimum expected level for all of us involved. Dont you think?
Safety is our concern. Do you not agree.
When ATC workload gets high, mix that with bad wx and having a guy constantly switching languages, it does go wrong. And instead of as you said, "decrease their ability to express their real time meaning and understading" it goes the same way but in english.
Dont think german is more strict than english at all. You dont think they have accents? Hahahaha
Last but not least, I leave that arrogans and monetary BS of yours to battle out with yourself. It was such a stupid comment of bring up capitalism on this thread- where did that come from?