Valuable user insights are gleaned from interviews, focus groups, surveys and rating scales. It's very easy to interview someone or hand them a survey, but it takes exceptional communication skills to ask the right questions that will result in a design that meets their needs, sometimes in a manner they could never have anticipated.
These customer insights are used to generate personas and journey maps. These artifacts help focus design efforts on the users, rather than the content, and are especially crucial for systems with multiple touchpoints, including ongoing service experience providers.
I have been a communication expert for over 20 years, and have published papers in peer-reviewed journals on a number of communication topics, including assistive technology, speech perception, and user assumptions when communicating verbally with robots.