Dogs have to be put on a leash when their outside, outdoor city cats should be too. Stops them from running away, and killing birds.
It probably does happen occasionally on accident, like hunting dogs that pick up an interesting scent and then get lost, but I’ve never met a good pet owner who’s pet ran away. It’s always the guy who locked his dog in the backyard 16 hours a day and never thought of them as family, or the cat owner who put the car on a starvation diet hoping it would catch mice.