Gonna toss in my two cents...
Why Lights out? Tradition. Before we had recording equipment and electric lights, it was tradition for ghosts to be out at night, to be summoned to a lone candle flame or warded off by bonfires. The night is going to eat you and all that fun stuff.
Why do we do it now? Cuz darkness makes for better TV than light does
I like the way Colorado and his group goes about things, checking it out day and night. I'm of the like notion that if ghosts are gonna pop up, it could happen at any time.
Yes, I am a cynical and jaded jacknape. I try to see all three sides of the coin- do you?