You can thank the Fed & Dodd-Frank. It's not profitable for Chase to buy miles if Debit nets less than 1%.

The Fed’s bold move on debit interchange

Basically, big card issuers won’t be able to charge more than 12 cents per transaction for debit-card purchases, and under one alternative their fees might be kept as low as 7 cents per transaction. That’s a massive reduction from the levels we’re seeing right now, which can range as high as 2 percent.

This is a victory for Dodd-Frank, a victory for consumers, and above all a victory for merchants over the financial-services industry.