One of the most vexing issues in Biblical interpretation is the relationship between pshat, loosely translated as the plain meaning of the Biblical text, and derash, the additional levels of interpretation that can be derived from that same text. At times the two appear contradictory; as, for example, the Torah's obligation of "an eye for an eye". The phrase seems to imply just that, but has always been understood in our tradition as demanding monetary payment, and no more.
The central aspect of the Pesach seder is the mitzvah of sippur yetziat mitzraim, retelling and reliving the Exodus experience. The Rabbis chose, as the central text to tell the story, that of the farmers' recital of thanksgiving as he fulfilled the mitzvah of bikkurim.