It's totally a mind game. Buy Now, Pay Later sounds friendly and warm, like "Visit your dentist" instead of "Go see your dentist." You visit your gramma, and that's warm and love and whatnot. Debt and Credit (credit as debt, not as a credit of something you earned or was returned to you) sound bad, and it also allows them to hide what it is from the more idiotic of primates. Tyrone didn't buy it on debt, he just has to pay later!