Many times the battery costs more than the savings, even if you charged it up for free, say at a mall or mcdonalds or something. If there was a large savings the utilities provider would be doing it already. Well that's also why people are looking into cheaper energy storage solutions.
I'm going to disagree with you although I'm not an expert so you might be right.
My understanding is that there are large savings available theoretically at the grid level but the capital to build it is limited and the grid interconnects to make it work are limited.
So globally there are huge amounts of battery storage being added to the grid but this is bottlenecked by capital and grid connections. Oh and land/planning permissions.
Long story short, house level battery storage may be worth it for some people
