Frequently impossible to correlate data collected from different sources. One often make hypotheses based on measurement. Sometimes one can test hypotheses by further measurement. Source code inspection often yields a quick and conclusive explanation. Demonstrably successful fixes are significantly better.
Students graduate well-versed in the vendor systems.
Research results are directly relevant to the vendor. Vendors influence areas of research. Vendors enjoy a good, healthy reputation around the Universities. NDAs for students. We are not liable if they steal.