This is not true. In Germany bike lanes are only required to be used when there is a sign saying so (and when they usable and safe, which you cannot expect, sadly). By default bike lanes are optional.
While driving culture generally is terrible in Germany, in my opinion, with people driving way to aggressively, the situation may be improving gradually. The idea of having to keep some distance when passing cyclists seems to have reached some drivers. (From court rulings 1.5 meters is the absolute minimum)