Why do we eat lamb, herbs and matzah at Pesach? I've heard dozens of explanations and every year at Pesach time, I come across more, but the one I like best remains the one I heard a few years back from an old, old guy with a long white beard and a mysterious far away look in his star-sapphire eyes.
According to him, the sainted ancestors ate lamb, herbs and matzoh for the same reason so many of us go for the kugel, ie, it evokes a simpler, more romantic time. Even in late antiquity, there would have been something rustic and old-fashioned about hunkering down with the whole family to spit-roast a lamb over an open fire. The matzah, too, would have seemed primitive, and delightful in the way a bowl of overcooked beans and potatoes is delightful to so many modern Jews.
Though this explanation doesn't tell us why God commanded us to eat those particular foods, it may help those of you who doubt the divinity of the commandment understand why the ritual caught on. And even those of us who believe that there was an Exodus, and a divine charge to eat matzah and roast a lamb can catch a ring of truth in this explanation, even if it's entirely incidental to the commandment's real purpose.