I think the thing with the German comunity is that it's so big compared to other local comunities (like the French, Spanish, Swedish etc). They can stay in German comunities (and use their mother tounge) and still get a big imput, allmost like the English comunities. I allso think (but this might be a prejudice, and a prejudice sprung from being from a pretty English friendly country) that Germany is very focused on German as a language. They dub their films/shows etc, so they don't hear/use that much English in their day to day life. This allso makes them more prone towards sticking to the German comunity.
Simply a few thoughs on my side, trying to explain why things are what they are. I do agree with you though, we're both missing out. I wish I'd learned better German in school.