Most places where this can be done, it is already being done. The low hanging fruit for pumped hydro was all picked decades ago, and at great cost to the ecosystems it destroyed in the process - turns out that drowning thousands of acres in massive man-made lakes had a bit of an impact on the plants and animals that lived there.

Not saying that the benefits weren't worth the cost, that's a whole different debate. But there's little to no opportunity to scale this energy storage tech beyond it's current footprint.