Grid Forming Batteries are a thing - but since it's not free to implement of course such a provider would like to get paid, not give it away, whereas both a conventional thermal plant or a hydro plant unavoidably has spinning metal, their stability comes free with the electrical supply.

The risk vs reward isn't great. If you made your country's 10GW grid work with only batteries for 15 minutes to show it's possible, maybe you get one half page in a "Electricity Weekly" industry newspaper. But if anything goes wrong and ordinary people notice - now you're on TV News for a week.