Lawsuits, the same reason for every dramatic AAMC change.
Let's say you're an amazing applicant who gets into Penn, Yale, and Hopkins. But you have your heart set on Stanford, who waitlists you. At some point Stanford looks at the multiple acceptance report, sees that you have three other amazing offers, and skips you. Lawsuit.
Let's say you are an amazing applicant who gets into Penn, Yale, and Hopkins. But you have your heart set on Stanford, who waitlists you. Eventually you reluctantly start orientation and Penn/Yale/Hopkins, but a few days in a seat comes open at Stanford. You are at the top of their waitlist, but they give the seat to someone else because you have started elsewhere. Lawsuit.