There are times where vending machines piss me off. Not only that, the people who service them (Vending Machine Administrators?) know damn well what they're doing.
Two vending machines, side by side. One distributes snacks, the other dispenses soda. You walk up to the snack machine, insert your dollar, choose your snack, and get 50 cents in change. You step to the soda machine, and see the price of the soda: 55¢
You don't have a nickel, so while the vending machine breaks your spirit and laughs to itself, you're forced to break another dollar bill. The machine's master likes handling bills rather than change. This is done intentionally.
How about another scenario? You walk up to the soda machine first. You insert your dollar, and get 45¢ in change. You make your soda selection, and it tumbles down to the tray. You grab your soda, and step to the snack machine. You insert the appropriate amount of money and make your selection. The coil starts to turn, almost makes a complete circle, AND...
Your snack refuses to jump!
This is also done intentionally, usually by overfilling the coils. One of three things will happen here.
• You REALLY want that snack, so you beat the shit out of the machine until it relents.
• You REALLY want that snack, so you put another round of money in to get it. Whether one or two of your snack falls, it's still more profit for the vendor.
• You don't care about the snack enough to spend twice as much on it, or to beat the daylights out of the machine. The next lucky person to come along might stumble upon a "buy one, get one freebie", but either way, it's more profit for the vendor.