Charging is just a point. Cables must be over entire track system. And if you at any point in time decide that cables are more economical you can always put them over any part of the track where you think it makes economic sense and use them to charge. If we had lithium batteries first there's be scarcely any overhead cables anywhere.

Heck, in US they don't even bother with cables or batteries, just put a diesel generator and a tank on electric trains for decades now.

But if you still believe I'm very wrong, please do elaborate.