Aren't they still faxing documents all over the place? (AFAIK, you might have to do that from time to time in Germany as well)

They are, and they still rely on hankos (https://en.wikipedia.org/wiki/Seal_(East_Asia)#Japanese_usag...). There has been a recent push for "digital transformation", but it is still in the early stages.

True all.

At the same time, they had an early form of mobile Internet since they year 2000 (when most of the West didn't have internet at all, let alone mobile internet): https://www.wired.com/2000/06/its-a-wireless-world-in-japan/

Japan is ranked 4th/20th vs Germany's 23th/35th for mobile/fixed internet speed, so much better overall (and anecdotal evidence is that internet in Germany's countryside is rock bottom).

So Japan rather seems to me to _want_ to do their own thing (at least when it comes to preference for cash, although I agree that still faxing things is strange), compared to Germany which _cannot_, for various reasons.