Tell me about it, as a native English speaker living in Germany. This happens even when the website has an English language version. I don't understand how they think this is helpful. My browser literally told you the language I want to be served in its first header!
Related gripe: Twitter will only offer the report form (for e.g. a harmful tweet) inside Germany, in German. I do understand conversational German but not German legalese; I will not bother to select which exact subparagraph of the communications legislation the tweet violates, I will just close the tab and let someone else report it.
RE:Twitter, I suspect that's because Germans get a different report form than other visitors - Germany has some specific laws (e.g. NetzDG) that apply to visitors from Germany, rather than visitors who speak German.
Related gripe: Twitter will only offer the report form (for e.g. a harmful tweet) inside Germany, in German. I do understand conversational German but not German legalese; I will not bother to select which exact subparagraph of the communications legislation the tweet violates, I will just close the tab and let someone else report it.