> They kinda do via net metering tariffs and curtailment.

They don't own your system through net metering. If you have net metering you are using the grid as a battery, which has a cost - the infrastructure to support net metering isn't free. For a long time residential solar customers (like me) were being subsidized for the upstream load we put on the grid.

> Now if one could get spot prices and sell your power then...the system gets more interesting.

They are running a pilot of this in California (PG&E): https://www.pge.com/en/account/rate-plans/hourly-flex-pricin...

It's currently restricted to downstream only customers. They plan to admit net metering customers to the pilot in the future.

Even outside of that, anyone can enroll a home battery in a demand response program to make money by supporting the grid during peak hours.