writing in the middle of the night

I would like to know why, exactly and explicitly, characters want to talk in the middle of the night.  Don't they sleep?  Ok, if they are my creations, there is no need for them to sleep, but shouldn't they respect my need for sleep?

Then again, the call of the muse, or the flute player, comes when it comes.  It plays the tune it chooses and hopes it reaches the ears of the intended.

Until I can better tame Kokopelli, the humpbacked, flue playing, fertility god, and evidently my muse likes his songs, I will answer and type when he dictates.  I won't necessarily type what he dictates.