They don't realized that they feed power back into the grid. This causes a safety issue with linemen working on repairs. Also, since these are not reported, the power company doesn't know it is happening. Home solar installations are coordinated with the power company, so they can take them into account during service. Main line cut offs are installed in case of power failure. Plug in ones have no built in safety features. Since people are using the power during power outages, they don't unplug them.