The history channel ran a program called the canine conspiracy where they pointed out that canines have become the perfect parasite of humanity. Now that I think about it, the cats are light years ahead of the dogs in terms of how to be the perfect parasites. Dogs need to learn how to do tricks and please the people who feed them. Cats just do whatever they want and most cat owners would actually have to bend over backward to please their cats.
My brother and his family have 2 cats and 2 dogs. The dogs stay in a cage whenever the nobody is home. The cats get free roam of the house. Whenever the dogs need to go outside, they get to stay only in the fenced in backyard. The cats get to disappear sometimes for days and then come back for free food. As far as I know, the cats have been sleeping in the same bed as his kids while the dogs get to sleep in the kitchen.