Kids can know to close the door, intend to close the door, but still fail to realize they didn't close the door. They're kids, it happens. And its a simple feature that can help realize the door is still open. It's not that deep..
My dog is my alarm for when the kid starts drawing on the walls or breaks something. He barks to let me know. It’s very convenient and I’m glad to have him. If it was practical to make a computer to do this I’m sure people would find it useful.