And the reason for that is that Medicare (CMS really) pays for all the residency slots. There is pressure to keep the Medicare budget from growing too fast which translates to slow/no growth in residency openings.
Providers with billions of revenue could easily afford to fund slots. They'd probably even benefit financially from it.
So refurb gave a reason for a bottleneck, and now we need to figure out why providers apparently aren't taking steps that address it.
I don't know enough about how hospitals operate to understand why that's a good/bad idea.