You’ll end up main connections and smaller ones to reach smaller destinations. This doesn’t mean it needs a single center like Paris. Compare the map to Germany where there are roughly 3 parallel fast North-South lines not focused on a single center.
Population in France is much more concentrated around Paris than population in Germany is. The Paris metro area accounts for 20% of France's population, while you need the biggest three metro areas in Germany to get to that percentage. Also Germany has double the population density, so even the less dense parts have more people.
It's actually not just population density. A big part of it is economic and bureaucratic activity. In France everything is centred around Paris, in Germany that's very different, e.g. Berlin is not a very big economic hub (although that's changing somewhat).
> Also Germany has double the population density, so even the less dense parts have more people.
That is not causal.
Some countries have a higher population density, but the population is mostly concentrated in one area and the low density areas are really low density.
I presume there is a standard way to compare density distributions between countries.
