>>11089482Medical licensing is done by the College of Physicians and Surgeons. They have an interest in reducing the supply of doctors, thus increasing their own wages.
Due to how big of an investment med school is, prospective students are going to want a guarantee that if they enter med school, they'll become doctors. Students will pick schools with high passing rates. The easiest way to have a high is to select only the people who are likeliest to pass.