While others are correct to point out that such a law would create perverse incentives, it's worth noting that debtors can already effectively buy their debt for a fraction of the price though settlements.
I'm not seeing it, and nor would anyone else who relies on good credit to, e.g. buy a car anywhere other than one of those weekly payment or your car won't start places.
So, anyone who disagrees with you fails to see the value of good credit?
The problem with your argument is that we're talking about people who've already harmed their own credit, probably for reasons out of their control. It turns out that people screw up their credit for all sorts of reasons, even though they presumably understand that it's harmful.
Incentive is only perverse if it would induce an otherwise non-defaulting debtor to default to get his debt to be sold at a discount.