The reason being is that periods of calendar weeks are used in the business world in Germany, but not outside that much.
GO knew this and as the niche market (unusual complications) is a strategy of GO, not many were built.
It is also a quite good prestige piece for GO, a demonstration of their expertise.
Further, as you said, people have to appreciate such technical effort.
Many gieve up and raise their hands and say :"To complicated!" (without trying to understand it.)
It is a true collector's piece, simpky speaking