You do realize that all that is also expensive, and limited? We haven't invented room temperature superconductors yet, and battery technology is far from perfect. There is only so much lithium and cobalt in the entire world. Yes we can now use things like sodium, but that's a technology that's still young and needs more research before it's full potential is realized. There is also a reason we have overground cables and not underground. Digging up all that earth is hella expensive.

You really don't understand how expensive underground cables are. You know those big, huge steel transmission towers that you see lined up, hundreds in a row?

Those towers costs hundreds of thousands or millions of dollars each. And the reason they're used is because that's way cheaper than underground.

Shit - just the cable is a couple million per mile per cable.

Because superconductors are even more expensive than breeder reactors.