Dieter Rams has been successful because he deeply understands people, both physically, psychologically, and how they operate in the world. He’s not some sort of mind reader:
You cannot understand good design if you do not understand people; design is made for people. It must be ergonomically correct, meaning it must harmonize with a human being’s strengths, dimensions, senses, and understanding.
Vitsœ’s direct contact with its customers has led to a deep understanding of people. Over the years, our understanding of how you use a shelf or an armchair has increased. We have educated and diligent people worldwide who understand how to plan systems in configurations that our customers may not necessarily have thought of at the beginning.
Good design, like any business, requires constant contact and feedback from customers. For more good advice, check out the whole speech.