There’s a cost to maintaining the grid and it was easy to just charge a delivery or grid fee per kWh but with battery that doesn’t work, not unlike fuel taxes supporting roads (in theory).

In Australia, there is a split between generation and sales. You have generation-and-electrical-distribution companies, and then you have retailers who purchase MWh in bulk from those companies to resell to consumers. There is a market for electricity where the spot price varies wildly depending on what supply dominates at any particular time.

For the consumer this boils down to an infrastructure fee of approximately AUD 1.10 to 1.50 a day, and then metering is usually anywhere between 0 to 50 cents per kWh, both depending on your plan and the time of day.

So I can get plans where electricity costs me nothing at certain times of the day, but then costs me 60c/kWh from 4-9pm, so I set my EV to charge during the day and stop during that peak period. I can go and buy a battery and hand over control of it to the retailer, who can use it to balance their MWh purchases from generation. Then sometimes you can get $30 in a few hours during peak evening time from your retailer when "cheap bulk electricity" is absent and they can sell your battery energy on the spot market for $$$.

The whole system gives a lot of options, and while it's no doubt not the best solution, it's something workable for the future.