Here are some of the advantages of a dog walker: 1) The pet remains in familiar surroundings - same bed, same smells, same toys, same food dish, same water dish, etc. throughout the day except for the time of the walks.
2) If there is more than one dog in the home, the cost of dog walking can be much less.
3) The pet owner is not inconvenienced in having to take and pick up the dog(s).
4) The pet owner does not have to worry if running a little late getting to the day care.
5) The pet gets one on one personal attention from the dog walker. The dog walker does not have to deal with 20 or 30 dogs at a time.
6) The dog walker and pet can develop a trusting relationship. Even where more than one dog walker is involved it is still fewer people (and hopefully much less turn over) than a pet encounters at a day care.
7) Since the most dogs we walk at one time is 3, your dog will not have to interact with large numbers of dogs for long periods of time and if necessary your dog can be walked by itself or just with your other dog(s) avoiding the stress of being around a lot of strange dogs.
8) In dog walking, the route may be changing a lot which is more interesting for your dog.
9) The dog walker and pet owners have more of a relationship.