Not a troll question, so please bear with me... From the perspective of the author of a piece of software wanting downstream changes contributed back, I think

Not a troll question, so please bear with me... From the perspective of the author of a piece of software wanting downstream changes contributed back, I think GPL makes total sense. From the deontological perspective of a consumer that considers closed source code immoral (aka Stallman's view if I understand it correctly), it doesn't make much sense to me. Consider the example where you go to a bakery and ask for a cake. Most people, I think, would agree that it would be unreasonable for a buyer of the cake to consider it immoral that the baker doesn't release the recipe to the cake. What makes software special?