Pesah - Haggada
Maggid - Mah Nishtana
We have the children ask the series of 4 questions pondering why this night is different than all other nights.
Why do we have to ask this question? It is different because it is Pesah! Every holiday has its special laws.
How come we do not make the kids ask on Sukkos why we are sitting in a sukka and waving a palm branch? Why on Shavuot do we not make the kids ask why we stay up all night?
What is different about Pesah that we require such questions, when every holiday has its "different" customs?
The difference is in the point of the night. On Pesah, the whole mitzva is "והגדת לבנך" - and you should tell to your children. The mitzva of the night is education. The transmission of tradition and history.
That mitzva of education is best accomplished by having the participation of the child. Having him ask questions.
It is true that during the other holidays we also wish to transmit tradition and teach our children, but on those holidays that is not the ultimate goal.
On pesah the ultimate goal is education. Education requires questions and answers.