The problem with this incentive is that it would encourage the university to only accept applicants who have a good financial background to begin with. For example, applicants whose parents have significant assets. We don't like to admit it, but this would probably be as useful a predictor as to the student's income as the quality of education.

If universities started choosing applicants this way, we end up with a system that reinforces generational wealth, rather than lifting folks out of poverty. No easy solutions here.