For example, there are probably 10-20 qualified applicants for every vacancy in medical school. Many highly motivated and talented people wind up going into other fields. Since the prospective students presumably either have or can get the money to pay the tuition, and are willing to pay the price, more instructors can be hired, more classrooms can be built, or more schools can be created and built. Assuming that our educational system is sound, and our testing and licensing systems are reliable and valid, the quality of the graduates will not be reduced. In fact, the quality will probably actually increase, since the motivation to become a physician or nurse will be an interest in the field, and desire to help others, rather than just a way to get a high-paying job.
Chiropractic colleges accept virtually all qualified applicants.
The system weeds out those who can't complete the curriculum or pass the licensing exams. The number of chiropractors is controlled by the market. If the number became too large, and chiropractors were unable to earn a satisfactory living, fewer people would enter the profession. The same rationale would certainly prevail if enrollments were opened up in medical and nursing schools. An additional benefit derived from the increased number of medical and nursing students, would be a stimulus for the construction industry, and all related industries affected by construction, because of the requirement to build additional schools.