I have heard people I know talk about cats that act differently. I think you believe dogs are unique because you choose to stay near them, and therefore know them more.
And I've heard many instances of murderers, that means every person is a murderer!
I searched Google, there aren't that many cases of cats leaving on a whim. The articles could be one-sided, the owned could be mistreating the cat.
What do dogs do, sniff well?
Some people don't want to walk a dog 2-3 times a day.