Symbolism, Imagery, Allegory
Just reading some of these tales is enough to make one's stomach start growling. There's a pot that makes endless amounts of sweet porridge ("The Sweet Porridge"); there's a table that covers itself with any and every kind of food ("The Knapsack, the Hat, and the Horn"); there's a supply of bread, meat, and wine that never runs out ("The Raven"); and there's an endless feast that only someone with an extraordinary appetite can consume ("How Six Made Their Way in the World"). And let's not forget the poisoned apple in "Snow White," the gingerbread house in "Hansel and Gretel," and the cake and wine being brought to Granny in "Little Red Cap."
Why the preoccupation with food, other than that it's delicious? In many cultures, food is a concrete representation of social networks and relationships. When one of the sons in "The Magic Table, the Golden Donkey, and the Club in the Sack" returns home with a table that will magically feed people, he proudly tells his father, "Just invite all our relatives and friends. I'll provide them with good refreshments and a fine meal. My table will give them more than enough to eat" (The Magic Table, the Golden Donkey, and the Club in the Sack.128). And when the heroine in "One-Eye, Two-Eyes, and Three-Eyes" is practically starving, a maternal helper-figure gives her a goat that will magically feed her.
You know the saying, "the way to a man's heart is through his stomach"? That goes for more than just courtship rituals; families feed each other as an expression of love and caring, and people celebrate holidays and special occasions with food. Exchanging food is a social act, so being able to feed people just because, as the magic tables and porridge pots of the tales do, is something really special.
Also, most of these tales originated from and were told by peasants. And agricultural life was harsh, yo. There was no guarantee that you'd always have enough to eat. So it makes sense that in "The Crumbs on the Table," a rooster urges the hens to pick crumbs from their mistress's table while she's gone. She returns and they get a beating. If we put on our metaphor-goggles, this seems like a pretty good analogy for the haves and have-nots of society; some folks are lucky enough to have plenty of food, while others are reduced to scrounging for crumbs at the risk of their own safety.
Having enough food is, by most standards, a good thing. Since fairy tales are about wish fulfillment, why not throw in a description of a good meal while you're also marrying a princess and being generally awesome?