Of all the rituals addressed in the Four Questions by the child on the Seder night, dipping seems to be least important. Unlike matzah and maror, it is not a Biblical or Rabbinic mitzvah; and unlike reclining, it does not express a central theme of the holiday.
How striking, then, that the first of the four questions addresses neither the first ritual the child encounters - reclining while drinking the Kiddush wine - nor the more essential rituals of the night, but a custom!
The Haggadah thereby addresses a misconception regarding the place of custom in Judaism. Some consider customs to be non-essential, a "luxury." They recognize the need to make sacrifices for mitzvot, but they would not do the same for "mere" customs. In regards to educating children, they argue, we ought to compromise on the customs so as to better focus on the primary obligations.
The Four Questions tells us otherwise. What is the first thing that the child asks about? What grabs his or her attention and makes the deepest impressions? Jewish customs. Not only are they not expendable, they are central. For the customs have the unique capacity to sensitize a child to the sanctity of Torah and mitzvot.
The customs give our children a strong Jewish identity and the sense that they are part of a nation chosen by G-d to be beacons of goodness and holiness in this world.
--From The Passover Haggadah By Rabbi Yosef Marcus