Medical schools do the same thing, but that's also what's causing a burden on the medical system. I truly blame most of the medical expense increases in the U.S. on them and medicare (which sets a base price and everyone else must make up for).
Basically there was a medical school student freeze[1][2] from early 90's through 2010. Now, it's finally starting to increase, still much less than population.
[1] https://www.kff.org/other/state-indicator/total-medical-scho...
[2] http://aamcdiversityfactsandfigures2016.org/report-section/s...