To come up with a proper design, UX designers use a lot of different research techniques, such as contextual inquires, interviews and workshops. They summarize research findings into user stories and user flows and communicate their thinking and solutions to the teams with artifacts such as personas and wireframes. But somewhere in all of this, there are real people for whom the products are being designed for.
In order to create better products, designers must understand what’s going on in the user’s world and understand how their products can make the user's life better. And that’s where storyboards come in.