What do dogs enjoy smelling so much at the dog park?
If you observe most dogs closely, you will see that the vast majority enjoy tracking and taking in smells in the park. They are cataloging which dog recently visited and its sex and state of health. They are locking all of that away for future reference.
A dogs nose is easily the most sensitive and accurate sense that it has. Philly parks are no more spectacular for dog smelling than any other park in America or the world, but parks are vital for any dog, particularly for satisfying their nose (and brain).
When you are on a disciplined dog walk, they say you should never let your dog continually sniff the ground, as that is giving in to what they want to do, and they are disrespecting you as the leader. It also means that they are not concentrating on bonding with you, and recall off lead will become more of an issue usually.
A big hint as to why smell is so important to dogs
What do dogs do when they first meet each other?
Social dogs walk around the side of the other dog, and sniff their butt. They are actually aiming for the scent gland, that in social dogs will be on full display. That is, happy or excited dogs will have a wagging tail that dispenses the very potent smell from the anal glad of dogs. This is really where the strong calling card smell comes from in a dogs urine.
If a dog is scared or doesn’t want other dogs to know they are around, you will see them with their tail between their legs, inhibiting the release of the smell of this strong scent.
Of course some dogs are better at smelling then other dogs, Dogs made for tracking or retrieving have the best sense of smell, as developed by selected breeding by human breeders throughout the ages. Likewise you will see that sight hounds such as greyhounds and whippets rely much more on their vision than their nose to get information.
The whole point of this article is that dogs rely on and absolutely relish using their nose to find out information about the world. Unless you are taking your dog for dog training or a disciplined walk, you should let is sniff as many things as it wants. A bored or unbalanced dog are the main kinds that you will see not using their nose to maximum effect in dog parks!