They have not. Acceptance rates are increases. The school makes more money by having more students.
While this may be true for public universities, private maintain their prestige by student faculty ratios and keeping their incoming classes between 1000-1300 students. You will see most private universities have kept their class size constant in the passed decade while public ones have increased, further supporting the graph shown in this article attesting to the disparity in grades between public and private schools.