The Ancestors were not meant to be served but deserved to be respected because they transmitted and protected Life for all generations to come. It is important to respect all the deceased and the Ancestors who preceded them in the afterlife.
Father Rahajarizafy Antoine de Padoue wrote it in his book: Philosophie Malgache (pp. 124-151), and he clearly says that the only one to worship is Andriananahary. On the other hand, he says, the Malagasy have seen the light in the Christian religion, completely reassured its spirit and completely satisfied it. It is therefore right that we respect those who have passed away and remember them specially every year and every Monday. They gave and left a good example to follow, as they committed themselves to physical and livelihood development, lived heartily and peacefully, lived spiritually and righteously. Therefore, all those who passed away interact with us every day and can also pray and plead for us.