Driver behaviour on the Autobahn is not some accident. Germany has the most expensive drivers licence in the world due to the number of lessions you have to take to even be allowed to take the exams, with most people opting in to even more lessons to pass the exams. To pass the practical exam you have to drive pretty much perfectly (a small number of people never pass). So everybody knows how to drive correctly and has it drilled into them at least once in their life how important that is. Obviously with routine some things slip, but nobody wants to get rear-ended by a car going 120 mph on the Autobahn either.