Twice during the Seder we wash our hands: first before karpas, and later before motzi matzah. The first washing has no blessing, and the second blessing has the traditional hand washing blessing: Al netilat yadayim. Notice that both hand washings immediately proceed food consumption. Even the ancients understood that eating food requires some sanitary measure. Therefore, we wash before the karpas veggies, which serve as an appetizer to hold our appetite through the long Seder. The actual meal will follow the blessing over the matzah, because in Jewish tradition, meals officially commence with the breaking of the bread, or in our case the matzah! Therefore, we wash with a blessing so that we can bless the matzah and kick off the long-awaited feast.