Have you ever seen footage of the Black Saturdays during the vacation periods on the German and French highways? Completely over crowded roads, traffic jams up to 100 km. At the gas stations waiting times up to 10, 20 or even 30 minutes are quite normal. And then we are talking about a fill up time of maybe 5 minutes per car. I wonder how many supercharge stations would be needed to replace one gas station.
You cannot compare German with French highways, because those are totally different beasts.
German highways are toll free for normal cars; French highways are not, unless you are nearby one of the metropolitan areas. France as a country in Western Europe has borders with 6 countries; Germany in the middle of Europe has 9, and is really a very crowded country, while in France all ways lead to Paris.
And since Germany is exactly in the middle of Europe, and given the nature of how "just in time" production nowadays works, there's a myriad of trucks, coming from all Europe, driving day by day on those highways, crowding them.
German highways can be really nerve-stretching, while driving French highways, like let's say from Metz to Paris, are one of the most boring experiences you can have in your life as long as you are not nearby a metropolitan area.
This here is a French highway, the A4 from Paris to Strasbourg:
The speed is being doubled, not much traffic, normally you only see another cars every few minutes, because the toll can be quite expensive. I did so this year in spring, from Metz to Paris, boring as hell. To the real traffic starts after the last toll station near cities normally.
The scene radically changes though, when you are driving the so called
Boulevard peripherique, which is the street around Paris, and one of its main arterial highways, normally 3-5 lanes, 90 km/h maximum speed:
Totally different beast, you must be either nuts or Parisian to drive this street voluntarily. It has got traffic jams all over every day, accidents and motorbikes driving with 80 km/h between cars, while there is a jam without shame, and drivers are normally quite aggressive.
And to put this into perspective: the city of Paris alone is quite small, its area is only 105,4 km² with 2,244 million inhabitants. In other words it has a population density (21000 / km2) and size roughly comparably to Manhattan (27500,3 / km2) in New York City, just without so much skyscrapers. The whole metropolitan area though is around 11 million.
Oh and by the way, the boulevard peripherique is officially no highway, but nothing more than a country road/route national.