Why do dogs like chasing things you have thrown?

Dog are descended from wolves that chased after mammals and birds for food, so the chase instinct is already present from birth. But domestication has also created a link between dogs and humans. Dogs actively seek play opportunities with us because they want our approval.

Consider the question from the other perspective: why do we like throwing things for dogs to chase? We like it because the dog enjoys it and we find its happiness rewarding. Dog and owner are engaged in a mutual back-scratching exercise, where the pleasure of one reinforces the pleasure of the other in a cycle.