Latest observed cultural gap: What's a credit card number?

I get calls every day from people who are incapable of figuring out where on their credit card their credit/debit card number is located.

I get calls from people every day who cannot figure out that all of the numbers on the front of the card are part of the card number. They seem to think that because the last four digits are inside the hologram they aren’t part of the number.

I seriously do not get it. These are people of every age and background. It seems like an utter impossibility to me that anyone old enough to have a credit or debit card would be so unfamiliar with them that they are unable to identify what the card number is or where it’s found. Even if they personally have never had a card before, how can they not know someone with a card, or have seen a commercial for a card, or seen one used in a store or in a movie or on TV?