According to Moses, the people were waiting for everyone to arrive so they could move the big stone from the well and give water to the sheep. It shows the importance of working together and being patient.
Genesis 29:8: And they said, We cannot, until all the flocks be gathered together, and [till] they roll the stone from the well's mouth; then we water the sheep.
This verse indicates the arrival and actions of Rachel which might contrast the previous verse's emphasis on the necessity of rolling away the stone first.
Genesis 29:9: And while he yet spake with them, Rachel came with her father's sheep: for she kept them.