Legally you do not need to, but I think it’s worthwhile to consider that debt doesn’t just magically disappear when someone makes a settlement.
The loss/cost is passed on to others.
I hear numerous radio advertisements about “call this number and we will get your creditors to settle for pennies on the dollar, owe taxes? We can get the government off your back and you won’t have to pay in full!”
If we make an agreement to pay of our own free will, then yes, we are obligated to pay it if we can. Passing the buck to others if we can pay is a moral issue.
If there is no reasonable way to pay the money back, because legal papers have been signed etc, then I would consider using it to pay a bill for someone who cannot, like heat assistance etc that power companies have.