Sometimes (a lot of times) when people bring their dog for training it's because the dog is not doing what the human wants.
Does the dog understand the desired behavior? Is the dog able to produce the desired behavior? Can the dog associate the behavior with the command? Does the desired behavior earn a better reward than other options?
If you were offered a job that payed better, payed more often, had better working conditions, greater chances for success, and more interesting and meaningful work, wouldn't you take it? And what if you were paid in cash?