Am I crazy? Is this NOT common knowledge?

The other day while working the SCO, I had a lady complain to me that she had no way of knowing that the machine she used didn't give cash back. I pointed out to her that it was a Card Payments Only machine that was clearly identified as such on both the idle screen and the payment screen.

She proceeded to tell me that she didn't know that Card Payments Only meant no cash back and that it should have been more clear. In my mind I start thinking that it should have been obvious to naturally logically conclude that Card Payments Only automatically means no cash back.

I reiterated to her that it does, and I thought my tone stayed pretty polite, but I guess my face gave me away because she told me "Don't look at me like that. It is NOT obvious or common knowledge. Most people don't know that."

I just apologized for the inconvenience and helped her switch to a machine that gave cash back. But, was she right? I've really always thought that it WAS absolutely basic, simple, and obvious common knowledge that no cash payments means no cash back either. Or is common sense just not so common anymore?