Why do great souls like Sai Baba take a physical form if they are beyond birth and death? What is their purpose?

According to Chapter 43 of the Shri Sai Satcharita, great souls and avatars like Sai Baba take on a physical form with the 'sole desire for the welfare of devotees.' They are described as personifications of Brahman who are essentially beyond the womb but appear on Earth for the sake of helping others. Their incarnation is not a result of karma like ordinary beings but is an act of will. The text explains that Baba appeared in Shirdi, gathered by the 'past merits of devotees,' specifically for their protection. The entire purpose of their rise and existence is the welfare of people. When their specific task is completed, they do not die but simply merge back into their true, unmanifest form, having fulfilled their purpose of guiding and protecting humanity.