At that point it's cheaper to buy a car with a smaller battery and use a stationary battery for grid storage.
There are plenty of scenarios where the EV makes more sense than a dedicated battery for it.
In my case, I live on a very shaded property; no solar for me. I also live next to an electrical substation, so extended outages from storms is highly unlikely; I'm first on the fixed list every time. In my case, the home battery doesn't make sense, but the EV might still.
EVs as grid storage is an option that may be compelling in some areas and for some people. I think that's worth exploring.