The sense of smell is how a dog takes in the world, and sometimes they're simply desperate for a chance to take a good sniff.
There are walks, and there are walks. It's definitely important to have a dog that knows how to walk obediently on a leash. However, it's also important to allow a dog to have some time to explore her surroundings while walking obediently on a leash.
Dogs see with their noses, and they place as much importance on their sense of smell as we humans place on our sense of vision or interpreting the world around us. It's probably safe to say that dogs appreciate the smell of a tree trunk the way we appreciate a beautiful sunset. Dogs loathe not being able to take in their world for at least a few minutes a day, and too often we humans are focused on going on walks for the sole purpose of exercise or potty breaks. We trudge along the same old route, often without any variety or sense of leisure, and in too much of a hurry to get back home again.
Do your dog a favor and dedicate one of your daily walks to having a "smell walk" — going slow and letting your dog take in the world with her nose. Go somewhere entirely new, explore a different neighborhood or trail, let your dog sniff at a spot until she gets her fill, even if it's for minutes at a time before moving forward.
For helping your dog know the difference between a walk where she should be obedient and stay beside you and a walk where she is free to explore, you can have a special backpack or harness that you use only for smell walks. Just make sure it is something very different from your usual collar and leash set-up so the different purpose for the walk is obvious to your dog.
These walks are a wonderful opportunity for your dog to get some of the mental and sensory stimulation that keeps life interesting for her.
Article by Jaymi Heimbuch: https://www.treehugger.com/things-humans-do-that-dogs-hate-4864319