Dealers have a line of credit, like a credit card, that they use to purchase inventory. They pay it back as they sell cars, and run it up as they buy new invent

Dealers have a line of credit, like a credit card, that they use to purchase inventory. They pay it back as they sell cars, and run it up as they buy new inventory to replace it. So the overall loan balance roughly represents their current unsold inventory. No inventory means no loan balance, which means no interest payments to the bank.