In Germany the written word has a higher level of binding character (commitment) than the spoken. Once a process – how the work is done – has been documented, and if done so in a detailed way, Germans feel obligated to work along that process in a strict way.
This reduces their freedom to deviate from the process, to improvize, based on the specifics of a given situation. For this reason, and a few other, Germans do their best to avoid documenting how they work.
The German self-understanding also comes into play. They often feel that it is simply not necessary to write down how they work. Germans are well-trained, tend to work in the same area for many years, are very familiar with formal and informal processes, can rely on the advice of their colleagues and management, and want always the freedom to work independently.
And German departments have a high level of institutional knowledge, which is passed on to younger colleagues. It is seldom necessary for colleagues sit down and document all of the things they do in order to produce good work results.