One of the keys to understanding this is that they requested H1B visas for far more overseas workers than they ever hired. There are only about 85,000 of these visas allowed per year, and (unless things have changed a lot since I got out of the medical personnel business in 2001) the biggest percentage goes to healthcare staff. I used to hire 4-6 foreign nationals (who graduated from US medical schools) at a time for the VA medical center where I worked, because there were no US citizen physicians who would work for the salaries we could pay.