Recently, the world's frist partial face transplant was performed in France. The recipient's labrador had bitten off part of her face while she was unconscious. Apparently, this is normal for dogs. It tried to wake her up by pawing at her, and when she failed to respond, it started chewing on her. Who knows when the next meal is coming, better to eat the hand that used to feed you.
If you fall and hit your head and get knocked out, maybe your dog will be heroic like Lassie and run for help. Or maybe it will eat your face. How do you know ahead of time if your dog will try to save you or grab a snack? You don't.
I haven't seen Xena in weeks and weeks, but now I think of her a bit less fondly. She never was particularly affectionate. Oh, sure, she seemed to love me while I was awake. But if she nosed me in the morning and I didn't wake up, would I become dog food? Possibly. Maybe when somebody else came home, she would run around excitedly with my head like sho normally does with a chew toy. It could happen. You don't know.
Your pets look at you like you look at them. In case of emergency: emergency rations. Can that really be love?