One example i ran into recently were concrete blocks that would be heated during periods of excess production, and then the heat converted back into electricity during slumps.
Never mind that smarter, nation wide, grids can allow electricity to flow in either direction depending on where the production and need is.
But every transformation you put your energy through between harvesting it and harnessing it has a cost, whether you are converting your electricity between DC and AC willy-nilly, storing it as chemical energy, or converting it to mechanical motion and storing it as gravitational potential. If you have a list industrial application that is not time sensitive, and is running at night from an 80% efficient storage mechanism (effectively, even if off the grid), you can boost your efficiency by 25% by running when it is sunny! Who wouldn't do that?
Larger grids are also more vulnerable grids. We should learn from the lessons provided by, e.g. the 2003 blackout in the northeastern U.S. We don't need bigger, more vulnerable, more tempting targets for the bad guys. We need more compartmentalization to limit potential damage and make systems easier to understand and repair.