It’s really important to realize that SEO is important for all of these kinds of content, but it is often only really considered for service-type content. SEO is often forgotten when it comes to credibility content like reviews, testimonials and case studies.
As a simple example, I recently renovated a Victorian-era house in the UK, and throughout the process, I was looking for various professionals that could demonstrate relevant experience. In this case, having a well-optimized case study showing renovation work on a similar house in the local area would serve as great long-tail SEO content — it also perfectly demonstrates that the contractor can do the job, which perfectly illustrates their credibility. Win-win.