I would imagine the requirement would be high foot traffic. Food has an incredibly short shelf life compared to other vending machine contents. That pizza vending machine likely has to be serviced/refilled/cycled every 2 or 3 days. The cupcake ATM would be slightly longer. Most of the cupcake ATMs are attached to the cupcake bakeries, but allow customers to buy from the ATM outside of business hours or when the line of customer is really long inside.