Maybe, but they supposedly (at least at that time) had that restriction on only a few types of prepaid cards - the ones I remembered in particular were Google Play and PlayStation Network - but other types were okay to purchase with cash.
Originally Posted by laserface
Google Play, Steam, and PlayStation Network cards are a favorite of overseas scammers who make a dishonest living by cold-calling feeble old ladies and explaining that the electricity/water/social security checks/etc. will be shut off immediately unless they head to the closest gift card retailer, use cash to purchase the amount of the alleged overdue bill in specific gift or prepaid cards, then read off the numbers over the telephone.
If I had to guess, requiring a credit card to purchase these items may be a way to shift the responsibility or handling of a potential claim of fraud or purchase dispute (on what is likely an already-depleted gift card) from the retailer over to the credit card issuer.