They say you get 2.5 miles a day or so in full sun. Lots of people drive only a few miles a day. I don't know if it actually matters, but for marketing purposes the ability to drive without the grid might be a good promo, especially when they can probably still bring the costs down a lot.

Hard to imagine a blackout so long that this would make a difference, that still involved having places to go inside the city, but in theory it could be useful.

Plus it's not from fossil fuel, which you probably care about if you bought an EV.