Ksav Sofer answers that the haggadah is warning us that chinuch needs to start on the ground floor, before a child is even old enough to ask. If not, an “aino yode’a lishol” is a rasha in waiting.
I love the Maharal in Gur Aryeh here. The “aino yode’a lishol” is not a two year old who is too immature to know how to ask and is not a simpleton who can’t ask. The “aino yode’a lishol” is the person who is simply too disinterested and/or distracted to be bothered to ask. In other words, he/she is your typical American Jew. What sin is he/she guilty of that warrants a response akin to that given to the rasha? Answer: the sin of apathy.
It’s a sin to go through life without asking questions, without pausing to wonder and think about our lot as individuals and as a community.