But the issue is that “more qualified” or “less qualified” is subjective, so framing this as weakening the criteria is flawed because the criteria cannot be objectively defined, despite the desire of many of those on this thread to do so. A higher class rank does not, by definition, make a student more qualified. Neither does a higher SAT/ACT score. Qualification is evaluated by the composite of the offering, aka holistically. And that lower rank, GPA, or SAT/ACT may be due to hours spent on some spectacular EC that classmates know nothing about.
From a school’s perspective, the attractiveness of the candidate may be impacted by the student’s actual interest in attending the school. When a student is admitted to their school of choice (I’ll avoid dream school) they might be more eager to attend and therefore be a better school community member than someone who feels they are “settling.” It isn’t just about accepting the best (ok, most qualified?) students who apply; it is also about creating a class that will represent the school well and take advantage of what the school has to offer. Those who end up at their safety or a target that they think is beneath them may bring that attitude with them or, worse, start at the school with the goal of transferring out. How is that good for the school? Choosing those who are perhaps better matched - qualifications-wise AND interest-wise - may result in a better overall result for the school. They may know that those they reject - those that many here say are for yield protection purposes - might not bring the right attitude to the school.
Often yield protection is done more with deferrals and/or waitlists and if those students truly want to attend the school, rather than just collect acceptances they will decline, they can demonstrate that to the school and, in many cases, that commitment will result in an acceptance.