Yes, there are many benefits to why dogs should wear a harness when they are out on walks.

First, a harness provides more control over the dog's movement. A harness distributes the pressure of the leash evenly across the dog's chest, rather than just its neck, which can prevent choking or injury to the trachea. This is particularly important for dogs with respiratory problems or brachycephalic breeds (short-nosed breeds such as bulldogs and pugs) who are more prone to breathing difficulties.

Second, a harness can make it easier to manage a dog that pulls on the leash. A harness gives the owner more leverage to steer the dog, making it easier to keep the dog on a loose leash, which can be more comfortable for both the dog and the owner.

Third, a harness can provide added security. For example, a harness with a handle on the back can be used to lift the dog over obstacles or out of danger, and a harness with a D-ring on the front can be used for training and behavior modification.

Lastly, a harness is a safer option than a collar for dogs that are prone to slipping out of collars or have a tendency to escape. A well-fitting harness will stay securely in place, reducing the risk of the dog getting loose or running away.

Overall, harnesses offer many benefits and make walking a more comfortable and safe experience for dogs. It's important to choose the right size and type of harness that fits well and gives you the control and security you need.