In locations with very predictable weather it makes perfect financially sense. Knowing when supply is high and when it is low makes predicting prices accurate, and the number of recharge cycles each year are fairly guarantied. Add a large amount of subsidies and it makes sense to continue building more of them.

Cutting down on subsidies removes a bit of the enthusiasm, but as long the other aspects are true then there is no reason why people would not build more storage when the financial aspects make sense.