That seems fairly obvious to me - SolarCity/Tesla have always talked about building a "virtual" utility via residential solar+battery, with the cars working as

That seems fairly obvious to me - SolarCity/Tesla have always talked about building a "virtual" utility via residential solar+battery, with the cars working as an (occasionally) mobile battery component. But the OP's question was why don't Tesla install MegaPaks that they own themselves, into diverse energy markets around the world - and become a traditional utility.