My thoughts exactly

Now as for the OP's problem, I have always been offered the snack box free when I asked... (^ on that UA) Really strange to hear they would neither give nor sell it to you!

Is there some chance that they put in the seat number on their little credit card machine, and that they aren't supposed to sell them in first? Must also look bad for the FA's to come up too short of snackboxes when they inventory them, so maybe that could explain why? Still no good in any case...