One of the main reasons why you want storytelling in your designs is because it encourages viewers to see more than a single image. The story should spread over multiple designs, and everything should be interconnected. This shows you brought a lot of thought and creativity into the mix, and people will be enticed to check all your work every time, which is very exciting.
Another thing to note is that storytelling helps change every viewer’s mind. It brings in more imagination and creativity. If you want people to step away from their day to day challenges, then storytelling and creativity are the right ways to achieve that. They give viewers a hit of oxytocin in their brain, making them happy and showing them that yes, your designs are worth checking out. If these designs sell a product, then the potential customers will show a lot more interest in what you have to offer.