I thought Tesla was experimenting to send AC through the earth . . . ?
He was experimenting with every way possible to do it NOT with wires. But the problem there is always efficiency at an absolute minimum. How much power do you have to put in the Earth or air or whatever 10 miles from me for me to get what I need here? Unless you assume you have more power than you know what to do with (and it’s cheap and you don’t care about any of the other potential consequences of doing that) that’s not going to work.
On wires, they are energized and I pull off what I need. Some does leak to the environment, sure, but WAY less than in any Tesla scheme. And the power company is constantly monitoring demand to make sure they put more energy than needed on the line, to handle any unexpected surge in demand, but as little more as possible to limit losses.
That’s not impossible to do with DC, and as others have noted DC transmission is sometimes a smart move if the receiver is running nearly zero motors. But at the same time, converting DC voltages is WAY less efficient and WAY more complicated what converting AC voltages - and when DC power conversion equipment fails it’s WAY more expensive and time consumer to replace/repair. So we live with an AC power grid.