The reason dogs are obedient is because they have been trained and socialized. Through training, dogs learn to recognize and understand the commands and signals used by humans, and respond accordingly. For example, a dog can sit by hearing the "sit" command or stop by seeing a hand signal. Socialization is also important as it helps the dog learn to get along with humans and understand human expectations. During early socialization, dogs can learn how to adapt to their environment and develop a trusting relationship with their humans.
In addition, dogs can also learn to receive rewards by interacting with humans, which can also promote their obedience. For example, if your dog wag its tail after hearing the "wag tail" command, it may be rewarded with some food or a game. This reward mechanism can help dogs learn to get along with humans and will be more willing to obey in future training.