Because a new service can provide people with an experience they have never had before, it is important to make it real and tangible. If you ask people to imagine a new service, they tend to become analytical and problem-oriented.
On the other hand, when people are allowed to experience a working prototype—something tangible that contains the key elements of the touchpoints and flow of the service interactions—they may react to the performance rather than the abstract concept.
— Service Design: From Insight to Implementation by Andy Polaine, Lavrans Løvlie, et al.