Besides the reasons others have already mentioned, load management comes to mind:
Getting rid of excess energy in the grid can be just as hard a problem to solve as to deal with excess load, and being able to simply and very quickly remove some supply from the grid is very useful for that.
Getting rid of excess energy in the grid can be just as hard a problem to solve as to deal with excess load, and being able to simply and very quickly remove some supply from the grid is very useful for that.