That's not quite true. You are allowed to buy games without an age rating in Germany, if you are over 18. However, the burden is onto the seller to verify your

That's not quite true. You are allowed to buy games without an age rating in Germany, if you are over 18. However, the burden is onto the seller to verify your age and it might not be publicly listed. So many resellers are not bothering importing games under these conditions, but they would be allowed to.