yeah, it is just a game, but asking that is like asking why would you want weapons or armor, or money, or why have food to eat, or be able to "harvest" flowers, and coal, and all that stuff.
I mean, what all can we actually DO with our raw meat? We can sell it, we can use it for summoning, and we can use it in like one potion(only one tha tI know of, there may be more), so why NOT be able to cook it?