This is mostly because the "Munich case" was a star example for a long time. Also, star division, the company that started star office, is from Germany.
That's why Germany is a great place that would adopt open source more, because they have prominent "own" projects like Suse Linux or that office suite. Now, nothing much has come of that in that way (but the German university I briefly studied at, did use Suse, of course).
