I don't follow the maths. A leasing company has a vehicle that they've got 15K "left" to pay off on, and they can only sell it for 10K so they'll just pay money to scrap it instead? How does that make sense for them?

If there is some monetary incentive for them to do this, you've not outlined who is paying it to them. And even if it exists, that's the problem, not the up front incentives.