Dogs have personalities too. Sometimes their personalities differ from breed to breed. I have noticed that smaller dogs bark more often and are much more noisy than bigger ones. They tend to get bothered by different things more so they also bark more. You can also think of it as being protective of themselves and their territory. It is also possible that dogs who bark a lot are protective of their masters.
Of course it is totally possible that a breed that is supposed to bark a lot can be quiet and a breed that is supposed to be quiet can be noisy. If your dog has been that way since day 1, perhaps that is what is normal for him or her. There are many dogs that don't bark much. If your dog is healthy, I don't think you have to worry about anything.
