It was the carrot cake that did it.
"What the? This thing doesn't have actual carrots in it. It's got got carrot flavored pieces."
"Really? What are they?"
"Umm... flour, sugar, carrot powder, coloring... other stuff."
"Maybe we should start making our own cakes."
"I doubt it's too hard. We should probably finish the stuff in boxes first, though."
"Of course. We just won't buy any more."
So, there you have it. No more cakes in boxes for me. Tubs of frosting, however, are necessary for the periodic graham cracker and frosting sandwich, so they'll probably stick around.