There are limited residency spots for med school graduates and if you don't get one you can't become an actual licensed doctor. The MD schools try to keep their

There are limited residency spots for med school graduates and if you don't get one you can't become an actual licensed doctor. The MD schools try to keep their admissions in line with the number of spots because that would be a raw deal to just pump out people with degrees in $500k in debt who will never get licensed. The residency spots are not controlled by the medical associations or the schools.