Why does my dog pull on the lead??

Every animal that has a backbone has something called a spinal reflex. What that means is that if you have a backbone, you will resist a steady pressure. Until and unless an animal has been TAUGHT to give to pressure, they will lean into the pressure. It's normal, it's natural, and it's reflexive. If you (the person) pull back, the dog will pull forward. If you pull forward, the dog will pull back. It cannot be avoided. It's what makes locomotion possible. When you see someone walking their dog and the dog is pulling forward and the person is pulling backwards, the person is forcing the dog to pull forward. The more strongly the person pulls back, the harder the dog is forced to pull forward. The dog has no choice in the matter. We might even say that the dog is not pulling forward, he is being shoved forward. A pulling dog is a problem that has been created by a person....

....If the collar isn’t helping, either it isn’t fitted properly, or it's being used with too much force (a flick of the wrist, administered with the strength of one finger is all it takes) or because the trainer is allowing the dog to lean into the collar or is forcing the dog to pull. Try to remember the next time you put a collar on a dog that you are training dogs, not catching fish.

To my eye, the clearest indication that the owner's pulling problem will be vastly more difficult to resolve than the dog's pulling problem is when the lead is wrapped multiple times around the owner's hand.

That is NOT finesse. That is NOT communication.
That is a clear commitment to PULL like hell.

This is referred to as the Suicide Wrap in horses.