They are bored
One of the main reasons dogs run away from their home is that they are bored. This is especially true of dogs that are indoors a lot of the time or dogs that need more attention and stimulation. Some dogs will literally just run away for something to do. If you are away from home a lot, consider hiring a dog sitter or dog walker to give them something to do while you are away.
They are in a new surrounding
Dogs are habitual animals who thrive on a consistent routine. If you are on vacation with your dog, or if you have moved to a new home in a new town, your dog may run away, back to the home they know. In this case, be sure your dog has their favorite blanket or favorite toy with them to ensure they feel safe and comfortable.
They are frightened
Many dogs are frightened by loud noises like fireworks or thunder. In this case, they will often run away to get away from the loud sounds. The best way to deal with this is to keep windows in your home closed during firework shows or thunderstorms, keeping most of the noise outside instead of coming inside.
They are excited
Just as loud noises can frighten dogs to run away, excitement sometimes scurries them away from home. Maybe your dog noticed a squirrel running down the street and decided to chase after it. The only way to really break this habit is through training.
They want to mate
Male dogs that are not neutered, may often run away from their home to find a female dog, who is not spayed, to mate with. Female dogs who are not spayed often don’t leave home to find a mate, because most of the males will come to them.