Imagine a restaurant branded as approachable and friendly - let's say the establishment serves comforting food in a warm environment at an affordable price point, but consistently provides rude, "off-brand" service. Bad service will alienate guests, but even more so if the service experience is incongruent with or contradictory to the brand.
Service quality studies have repeatedly shown that good service leads to brand trust and brand loyalty. While emphasizing service quality is important for all experiential businesses, high-touch businesses where staff frequently interact with customers - for example, when customer journey involves consumer education - have to be even more vigilant to their service quality and how their employees express the brand compared to lower-touch businesses. This is simply because there's a higher frequency of service-related touchpoints, and each touchpoint tells consumers something about the brand.
How can you design service interactions to promote a positive brand image? Hire brand-aligned employees who agree with your values. Consider them your brand ambassadors; if you want them to express the brand, they must first fully understand it. Share best-practice brand behaviors with your employees, so they can consistently deliver on-brand service. And hopefully this goes without saying - treat your employees well.
Service design is gaining mainstream recognition as a concept but is particularly applicable to experiential businesses. The following resource from the Interaction Design Foundation is a straightforward yet comprehensive introduction.