I worked for two years in a communication agency where I quickly realized that if you argue for your design with "because it looks good", it won't get very far. What makes a design untouchable is the story it tells in the background. As I started to make up for anything I designed a story or a thought I started to succeed at pitches. Because in the end you might not exactly remember the design, but the story might still stick with you.
Storytelling is a valuable tool used for communicating thoughts and ideas to the customer. A good story will be retold. Not only for television advertising it's important but in the whole field of design and communication.
But as everything storytelling has also it's dark side. It can be manipulative if used for the wrong reasons.