Why does the interest matter much if you are going to declare bankruptcy anyways?
From the individuals' perspective, overusing uncollateralized debt to be discharged is a good deal. That loss is offset by the creditor by issuing higher interest to unsecured credit lines because people can default on their debts. From the creditor's perspective, it's risk adjusted for people who default.
It just logically follows. I can't help you understand past this.