‘While he yet spoke with them Rachel came with her father's sheep, for she looked after them. And so it happened that when Jacob saw Rachel, the daughter of Laban his mother's brother, and the sheep of Laban, his mother's brother, that Jacob went near and rolled the stone from the well's mouth and watered the flock of Laban, his mother's brother.'
Rachel, who had previously been spotted some distance away (Genesis 29:6), now arrives. So Jacob gets his men to help him to move the stone so that the flocks can feed. He is not used to having to wait and ignores any custom. He does not want to have to linger. Or it may be that a brief discussion has revealed that the well is Nahor's so that Rachel has the right to secure its opening. (Jacob would not kiss Rachel without at least some preliminary words).