At Jacob's well, the woman immediately notices two boundaries: Jesus is a Jew, and she is a Samaritan woman. John explains her surprise by noting that Jews and Samaritans did not ordinarily associate freely.
The exchange therefore begins across a division that the participants themselves recognize.
Jews and Samaritans shared Israelite traditions and reverence for the Torah but differed over ancestry, sacred geography, and the legitimate center of worship. Samaritans regarded Mount Gerizim as the chosen sanctuary, while Jewish worship centered on Jerusalem. Political and religious conflicts sharpened the separation over time.
The Greek wording in John 4:9 can imply lack of association and may also carry implications about sharing vessels. It should not be expanded into a claim that no Jew and Samaritan ever interacted.
The background makes Jesus' request for water socially significant before any theological discussion begins. He deliberately initiates conversation across ethnic-religious and gender boundaries.
John then allows that encounter to grow into an extended revelation of Jesus' identity and eventually into a Samaritan town welcoming him for two days.