What we find is that over time the rituals changed. What is common is that people entered the tombs from time to time, maybe on a yearly basis, and recontacted their ancestors. They may have pulled the bones out of the tomb and rearranged them but it was a ritual where they could contact and pay respects to those who had died. Some believe that the megalithic tombs of England may reflect a symbol of the earth's fertility (see the legacy of Stonehenge).
In a larger sense there is much we can learn from Malta and Gozo. There is a dimension of social change that is reflected here in these ruins. It is a society that has no cities and is based on farming villages. The temples and tombs are the means by which society was held together collectively. These were places of religious significance that people could share. It was from these central places - religious places - that unified people. It is similar to what one finds in the cities of India where people made pilgrimage to these places thereby unifying a very large population that lived in villages spread out over a large area. The Malta and Gozo tombs brought people together in common cause. They may have been a place of leadership and power in a sense too.