It was for privacy reasons, which is why so many houses are also blurred. Once a house is blurred there's no way to unblur it since Google doesn't take new pictures and as far as I know the blur would still stay at that spot.
Look at every country around Germany and you'll see a web of streets covered by Street View. In Germany it's one big blank [0] and what's covered uses decade old pictures taken before Google stopped mapping Germany on Street View.