Have you ever wondered why your dogs favorite treats don't always do the trick in high stress situations? Something to keep in mind throughout your training process is the level of value your treats hold.
Think about it in terms of money. You might be willing to do one easy task for $5, but then you are asked to do something significantly harder for the same amount of money... You probably are going to say no. But if the pay were to increase to match the job, you would be more willing to complete the task. Think of your dogs treats as money. Kibble holds the lowest value, because they get it on a regular basis.