Q) Why do we even eat and dip Karpas in the first place?

A) There are 2 answers:

1) to remind us of the tears from the Jews as slaves in Egypt. 

2) The Gamarah says: on the Seder we overall, just do weird and unusual things. Now why do we do these abnormal things? So the children will ask!! BUT, then why is it that all year children aren't obligated in any Mitzvot and now, all of a sudden the ENTIRE Seder revolves around them?!?!

So, like the Gamarah stated, at the Seder, we do weird and unexpected things. It is an obligation for one to feel like you are leaving Egypt. Imagining is very difficult for adults. BUT, for children, it is very easy to imagine things. 

Therefore, if the kids tell the story to us, then it will help us, the adults imagine the story of Pesach even better.

Chag Sameach!

haggadah Section: Karpas
Source: My Teacher