If you consider that EVs have A) large batteries w/ efficient charge/discharge cycles, B) efficient high-capacity inverters, and C) are plugged in (somewhere) for large fractions of their life, and D) very often have capacity far exceeding their next expected trip duration, then:

It is inevitable that Tesla (or someone else) will implement Grid-tied battery backup as a standard option on these vehicles.

When that happens -- the Grid gets "free" multi-GWh battery-based load shedding.

Why is this not considered an inevitability? Am I missing something obvious here?