What is the difference between writing about worldly leaders and writing about saints?

According to the preface in Chapter 0, writing biographies of worldly figures like leaders and writers is considered a worldly service that is limited by time and space. Even if it involves public education, it is rooted in self-interest and does not yield spiritual fruits. In contrast, writing the biographies of many saints is a form of Guru service that does yield spiritual fruits, although it is considered a partial or one-sided path and not sufficient on its own to attain the ultimate spiritual goal.