It is an absolutely fundamental element of independent investigatory powers for this kind of office to have the power to compel documents and testimony. Often, really key information is in the hands of companies, and without the ability to require companies to provide those documents and testimony, it simply won't be part of the investigation, and the rest of the office will crumble. You can't make effective recommendations without information.
On February 23rd, 2021. See this statement in context.