Actually I don't believe that's true. You may be making the payment 30 days after the purchase, but in some cases it takes merchants like 60 days to get paid, so the CC guys are STILL getting paid before the money has to go out, and can collect interest in the meantime (in addition to the 3% or so of the transaction in the first place). They seem to have all the angles covered.
Good point, I didn't think of that.
But the part about the person with the card not paying any interest is true. And deadbeat is an insider term they use as I described it.