If a Sadguru's desires are already fulfilled, why does he accept offerings from devotees, according to Chapter 16?

Chapter 16 explains that a Sadguru like Sai Baba is "Aptakama," meaning one whose desires are already fulfilled and who needs nothing from a disciple. However, the chapter clarifies that the Sadguru accepts service to fulfill the desire for service within the disciple, which in turn helps make the disciple desireless. The attitude behind the offering is paramount. As noted in Chapter 16, if a leaf or flower is offered with sincere faith, He accepts it with great love. Conversely, if an offering is made with pride, He will turn His face away, as He is an ocean of Truth, Consciousness, and Bliss who values sincere faith far more than outward rituals.