Seriously? My dog doesn't go out by himself because I'm scared he'll get stolen, lost or hurt. He's a beautiful auburn staffy, and, although he's neutered, someone could try and steal him for breeding purposes. Or fighting/status dog purposes. Plus he's a big softy and would get scared/upset by himself out there. I've hidden before when we're out on a walk, and he looks around frantically and runs about looking for me, so I don't think he'd cope out there by himself.
I wanted my cat to be an indoor cat, but my pets live with my Auntie around the corner and she didn't want the cat to be cooped up inside. So she goes out, and she's always in for the night. We don't let her out at night.
She's also spayed, microchipped and has a collar. She doesn't tend to go far.