

You do. But you also plan in the case the surrounding infrastructure fails.
But more to the point, in some cases it is better to produce (parto of) your own electricity (where better means cheaper) than buy it on the market. It is not really common but is doable.
Technically it is possible to have a system that is not based on Internet but with bluetooth. The problem is that it would be effective only if widely used. And probably would have a many more problems.