There's a lot of ways to store energy if you're basically getting it for free, and these are generally more efficient at scale. It would be great if a utility could help buffer this for you.
Yes, that's another reason why a municipal grid would be useful: city-wide storage could work better than each house having a small battery (but the roofs are still useful for panels, of course). But it may not need to be a utility in the traditional sense (unless the US meaning of that word is different from what I understand it to be). Just some local company with a contract. Or a few of them.
Here the power company was split up into a generation unit and a distribution unit. What you're talking about is having a third type, a storage unit, to help manage demand.
If you can pull power off the grid very cheaply, even get paid to "dispose" of it, then later return it at a profit, you could arbitrage solar capacity.