1. Exercise. All dogs need exercise every day, even the smallest breeds need to have a daily workout of their little legs. The larger a dog is, generally the more exercise it will need. There are working breeds, however, that are deceptively small but needs loads of exercise. When choosing a dog breed, do assess how much exercise it will need to make sure that you have the time and inclination to do it. You may be lucky enough to have a few acres of fenced land at your home that your dog can run around in but it is still important to take your dog on a walk regularly as there are several other benefits from the structured dog walk.
2. Bonding. A regular walk together with your 'best friend' will build and strengthen the bonds between you. Your dog is always exited and grateful to go out on a walk and will genuinely try to please you in order for the activity to be as regular as possible.
3. Training. The walk time is an ideal time to accomplish a number of basic obedience training tasks. Firstly, you are reinforcing your role as pack leader. Secondly, you have the opportunity when you are in a place where your dog can run free to train your dog in some basic commands, like 'come', 'sit' and, of course, 'fetch' This training will take the form of play for the dog and it will learn far easier than in the house.
4. Getting used to being on a lead or leash. All dogs need to be controllable and therefore all dogs should be trained to behave while on a lead or leash. This is valuable training even if you are fortunate lo live in an area where your dog can run free most of the time. There will come the day when your dog needs to visit a vet or you need to take your dog to the city and if it will not behave well on a lead, you will have problems.
5. Socialising. By being away from it's home territory, a dog is forced to learn some social skills around other people and other dogs. This is an important factor in preventing excessive aggression in your dog later on.
6. Avoiding doggie depression. Dogs that do not get a change in the environment frequently enough can become depressed. A depressed do can develop into an anxious dog and that can lead to behaviour problems. Regular walks, even if the follow a predictable path, will enliven your dog. It will be using all of it's senses to its fullest ability thus exercising its mind as well as its muscles.

Great post priyani