Some dog breeds are naturally more vocal than others.
Genetics also plays a role in how much a dog barks. Some dogs are simply more prone to barking than others, regardless of breed.
Dogs that are not properly trained may bark excessively. For example, a dog that is not taught to obey the "quiet" command may bark to get attention from its owner.
The environment can also play a role in how much a dog barks. For example, a dog that is bored or anxious may bark more than a dog that is well-stimulated and content.
In some cases, excessive barking can be a sign of a medical condition, such as pain or anxiety.
Provide plenty of exercise and mental stimulation. A tired dog is less likely to be bored and destructive.
If you are struggling to reduce your dog's excessive barking on your own, consider consulting with a certified dog trainer or behaviorist.