Mnemon: Answer is much simpler. German studios know the laws of the local market so don't produce anything that might be banned in the first place. For good or bad.
Geralt_of_Rivia: Nope, you are mistaken about that. German studios can create whatever they want even if they risk that they can not sell their products in their own country. Crytek (the developer of the Far Cry and Crysis series) for example is a German company.
Sure they can - but few do. Crytek is an exception - I really can't think of many examples where German companies produced something that might be in danger of being banned, otherwise. Up to interpretation if that's a case of self-censorship or just business sense.
If you look at the big successes - even globally of German studios, things like the settlers, battle isle, the variety of business sims that are / were big in Germany all don't even come close to being a problem.