Once made, a three tiered cake won't allow you to remove pieces from it. It gives a system message of "You do not have enough space for this in your backpack!" even when you are clearly nowhere near the item or weight caps. Since you can't take pieces while the cake is on the ground (which is counterintuitive) this makes using the cakes rather difficult.... Edit: If you have nothing, or virtually nothing, in your pack then you can get slices off the cake. This makes cakes rather unwieldy to use, thus most people won't bother.