The purpose for being able to turn the lights off when there is no power is NOT for the purpose of formal safe disconnection so that I can work on wiring the circuits. If I had a really compelling reason to start work on the wiring while the power is out, I would switch off the main service entrance disconnect breaker.
The big reasons I can see for wanting to turn the lights off are:
1. To prevent all the lights from coming on when you are away, wasting electricity and increasing your electric bill. This applies if you need to leave home during the outage. Some people like to keep their appointments or social/family engagements even if the power is off at home. Some people like to go to work even if the power is off at home. And some people might even choose to go out for dinner because they can't cook, because ... you guessed it ... the power is off at home.
2. To prevent all the lights from coming on when you are asleep.
The situation I had with the utility maintenance going on that knocked out the power was more of a fluke. I simply took no chances and disconnected all the computers (one pull of the UPS plug since at the moment only 4 computers are in operating state), stereo system, and 4 TVs. I then instinctively went to turn off all the lights.
Perhaps I should have switched off the main entrance breaker, too.
In a previous power outage, my father had a burner element on in the kitchen. He never thought to shut it off when the power went off, despite moving the food off the burner (he decided it was done enough to eat it). After the power came back on a couple hours later, the burner stayed on, without a pan on it, for about a couple more hours. Fortunately it was on low.
So now I remember to also check the stove (which I did during this most recent event).
I did a quick survey of my 3/4-way light switches today. 2 are off when all switches are down. 3 are on when all switches are down. 1 has a push to toggle on/off rotary dimmer switch as part of a 3-way setup, so there is no way to know if it is off or not since the pushbutton state is unknown without power. So I'm going to replace that rotary with a definite up/down switch with the side-slider for dimming.
