Pesah - Haggada
On Pesah night at the Pesah Seder we read the Haggada. The word, "Haggada" comes from the word "Maggid" which is the section of the Haggad in which we relate the story of the exodus. Maggid is the bulk of the Haggada. "Maggid" comes from the mitzva of "V'Higgad'ta L'bincha" - you must tell over [the story of the exodus] to your children.
The purpose of the whole seder night is והגדת לבנך. We have to transmit our history and tradition to our children. The next generation.
Most of the time we are busy. We are caught up with work, hobbies, even with our regular schedule of learning Torah. We are often so busy with our daily lives that we lose sight of our role as teachers of the next generation (a side note ala Rav Hirsch: the Hebrew word for parents is "horim" which also means "teachers").
We forget that we are links in the chain of Jewish tradition and history, and that it is our job to build the next link in the chain and ensure that it is strong enough to continue the chain unbroken.
The seder is that opportunity for us to take the needed time out from our regular schedule and focus on that chain. We have a special mitzva just to relate the focal point of our history - that which made us into a nation.
Sometimes, even then at the seder itself, we get so caught up with our own pre-conceptions, that we still forget the goals and objectives of the night. We get caught up with trying to make sure the seder goes just so, and we measure the matzas to make sure everything is exact and the maror and whatnot, and whatever other narishkeit we might get caught up in we still get caught up and lose sight of the objective.
So the authors of the Haggada have built into it safeguards to ensure that we stay focused on the real mitzva of the night. We do things that are unusual and sometimes even unnecessary. Things like "u'rhatz, karpas, etc". The reason for many of the customs performed at the seder is "so the kids will ask". Even if we get distracted and lose focus, the kids will stop us and bring us back down to earth and ask why we are doing what we are doing. They will give us the opportunity again to refocus our seder to achieve the desired objectives.