That's true on paper, but note that in the outer suburbs, towns are usually small and kids would have to ride quite long distances (>10 km) to get anywhere useful. And winters here can be rough. Add to that narrow streets and careless drivers, and I can totally understand why you don't see many kids cycling.
Regarding rough winters, I grew up in Germany and live in Sweden now, so saying winter in France is rough is quite funny (my French partner is laughing quite hard now)
I don't know where you grew up in Germany nor am I familiar with the country, but the places I've visited (in Baden-Württemberg, around Schwäbisch Hall mostly) had amazing bike infrastructure, with paved paths in very good shape and several meters away from car roads, separated by grass, dirt, etc. I can see why parents would have absolutely no problem letting the kids bike around these paths. Also, drivers seemed much less crazy than around Paris.
Let's also not forget how incredibly empowering bikes are for kids, essentially they can get anywhere they want to if they can ride around on a bike.
About French drivers, I have the feeling that French drivers are very inconsiderate to every one not just bikes at least for urban traffic.