Re: And all because
The reason why they're really looking at static storage is that the cost/kWh of batteries has fallen dramatically in the past 10 years, and Tesla in particular emphasizes reducing battery costs. As other people have mentioned, the marginal cost of electricity is stupidly high, due to the need to deal with instantaneous, intra-day and seasonal variations in demand, and that means that battery costs don't have to get too low to be able to used at the margins. Oncor, a Texas distributor, wants to spend $5.2B on installing batteries around the network from about 2018, estimating that as long as prices are below $350/kWh it would lower electricity prices slightly, and obviously, prices would be lowered by more if batteries prices fall more than that (and almost all projections see that happening).
Right now, because electricity pricing is totally stupid (paying for distribution costs by kWh instead of kW) and solar PV subsidized by net metering, a consumer battery could have a market, especially if they pass marginal pricing on in the consumer batteries.