According to the preface, why is writing about worldly figures like jurists or writers considered an inferior form of Guru service?

According to the preface in Chapter 0, service dedicated to worldly figures, such as writing biographies of politicians, jurists, or writers, is considered of a worldly nature. While it can be a form of public service and contain public education, its importance and fruit are not eternal. The text explicitly states that this type of service is limited by space and time. Furthermore, it is often rooted in self-interest, which is a key reason why it does not yield spiritual fruits. This is contrasted with service to saints, which is oriented toward achieving spiritual, rather than worldly, outcomes.