I now have a fenced yard and walk my dogs every day. They're older now and much easier to satisfy but they aren't calm lazy dogs so its not easy. But I couldn't imagine just opening the door and letting them run free. Even with reliable dogs who stay right in the yard, there may be a point where they spot a rabbit or some other distraction and chase them until they're lost or in trouble. Or maybe someone opens their car door and takes them. Or finds them lost and drops them off at a kill shelter, or keeps them. So many never return for whatever reason. If you're one of those people who insist your dog always comes back, I wish you the best but don't be surprised if one day they don't.