There are many reasons why dogs may run away and not come back, including fear, confusion, illness, hunger, or the lure of another home. It's important to ensure that your dog has a secure and safe environment when outdoors, so consider things such as fences, a leash when walking, and keeping them in an enclosed area when unattended. Also, always ensure your dog is microchipped and wears an ID tag with your contact information in case they become lost. Finally, if your pet does wander off and you can't find them yourself, don't hesitate to reach out to local police or animal services which may be able to help reunite you with your pup.