It's a curious industry in that the "good" customers are those who live on a knife-edge, keeping their cards at or near to their credit limits, yet usually just about managing to make the minimum payment each month but no more, and occasionally missing a payment.
Whereas customers who are financially sound and pay off the full balance each month are "acceptable" customers because the card issuers make some money off the margin charged to retailers, but nowhere near as much as they earn in interest from the "good" customers. "Bad" customers are those who regularly miss payments, exceed their credit limit. and become bad debts.
So a "good" customer can very easily fall over the precipice and become a "bad" customer without ever being merely "acceptable".
Mike.