Complete guess here but I would suspect that means some items are made in Germany and some are made in China or elsewhere (meaning, even the same model may be produced in both locations). If they are printing "MADE IN GERMANY" directly on it then it will be obvious which ones aren't, because they would lack the print. And that would likely degrade the perceived quality of those not made in Germany vs those that are. And Sennheiser doesn't want you to think that some of their items are built with better quality than others.

Of course, people can look at the fine-print and determine where it was made. But that's a lot less obvious than the silk screened badge not being there.