What is the message of the simanim of the seder? Just as a siman enables someone to identity a lost item, the simanim of the Seder are meant to enable us to find what Hashem wants from us.
The more we prepare for something the more we get out of the experience.
הא לחמא עניא: Why is the paragraph the only paragraph in Aramaic? Why are we inviting guests now! What is the connection between the different ideas expressed therein?
מה נשתנה: We don't usually eat chametz and matzah it's generally either or! The Korban Pesach is a Korban Todah but unlike a regular Korban Todah there is no chametz.
Why don't we make a bracha on סיפור יציאת מצרים? Because there is no shiur.