How is a 3.9 GPA business degree from a "top 10 ranked public university" relevant to operating a commercial airliner?

Whether you like it or not, airlines must clearly find better results with those candidates coming from aviation universities... or they would not be offering these bonuses. Aside from the actual flying, an aviation degree might also include curriculum in advanced aerodynamics, meteorology, human factors, flight physiology, aviation law... heck, even interpersonal communication. These are all subjects chosen to groom a well-rounded professional pilot and the results show.

Right now there are far fewer students enrolling in these types of courses. If airlines want to keep hiring from these universities, they will have to show some incentive to future prospects.