If they do, it could be because they want to feel more like part of the family, or it's just a particular animal's personality and that animal was matched with the person meant for it.
How come the invisible dogs are so much better behaved than real ones? When I run my invisible dog for agility (aka walking the course), he always qualifies. Well, except when I was running my invisible Jet the try-ing.
I LOVE It's Me Or The Dog!!! She is awesome. She really lays down the law for people. Especially when the family pack order is all out of whack, which is often.