this is sadly actually one of the largest use cases, it's called a dead-mans cable (for good reason) but it's how many northern residents run generators in the winter during power outages. Cheaper then running a bypass switch (which can easily be 300-500$ to buy plus install cost) by a huge margin. They just throw the main breaker prior to running the generator. It shouldn't be done but it happens more frequently then you would expect especially in the antiqued houses that may not even be up to code in the first place