As customer service shifts rapidly to the customer, the most common place you'll find this new system is at the self-serve payment kiosk. Cashiers, if there are any, don't want to handle your germ-laden card, so it's up to you. But interacting with a machine doesn't get you out of the customary upselling. After you pay for what you've bought, do you want to give us more money? You might think it would be easier to say "no" to a machine, but this guy finds that it's anything but.
And now we have self-serve kiosks asking for tips. A tip for what? No one served me; it's a self-serve kiosk. There's no one around except for the business owner staring at you from a seat ten feet away. You can't tell me he's making a sub-minimum wage. But that's the thing about payment machines- you can't ask questions. You can only answer questions. And you can't refuse to answer questions, or the transaction is liable to be canceled. -via reddit