Comfort of native language is undeniable, that's not even close to my point. Of course you would be kind and use appropriate local language whenever you can. It is that native fluency cannot be matched really as someone who learns the language at a much later stage in their life, and Germans usually have unreasonable expectations from immigrants to speak perfect German, especially when that said immigrant is also aiming for career advancement. Therefore everyone is being measured on their ability to climb a tree and while Germans are like monkeys, some immigrants are like fish. Speaking English in the work setting would level that playing field (many immigrants are not native English speakers, too), and it's one thing the German companies just wouldn't give up. Why? Work culture. Riddle me that.