why?

Here's what I want to know. How is it that the man laying next to me can fall asleep so easily? I'm telling you, his head hits the pillow and poof he's out. All the while I lie here next to him with my mind yammering on about this and that, keeping me awake for way too long. The house is quiet, except for deep breathing, occasional snoring, and the heater turning on and off, inside my head it's a circus.
As I'm laying, perfectly comfortable, and maybe, finally, drifting off, I hear a noise. I'm all ears, wide awake again. It's Conrad, whimpering in his sleep. Nothing to get out of bed for, but I keep my ears open, in case it should become a reason to check on him.
And then I think: "Why? Why is it that, even if I'm asleep, I pick up on these soft noises of possible distress from my babies?" And not so much "Why do I hear them?" as "Why doesn't Mr. Boss hear them? Why does he get to sleep soundly, uninterrupted by nighttime peeps?"
Just one of the many random things I'm thinking about as I try to fall asleep tonight.