The fact is that there is no shortage of science, technology, engineering, and math workers in the United States, as Michael S. Teitelbaum points out in his article in The Atlantic:
A compelling body of research is now available, from many leading academic researchers and from respected research organizations such as the National Bureau of Economic Research, the RAND Corporation, and the Urban Institute. No one has been able to find any evidence indicating current widespread labor market shortages or hiring difficulties in science and engineering occupations that require bachelors degrees or higher, although some are forecasting high growth in occupations that require post-high school training but not a bachelors degree. All have concluded that U.S. higher education produces far more science and engineering graduates annually than there are S&E job openings—the only disagreement is whether it is 100 percent or 200 percent more. Were there to be a genuine shortage at present, there would be evidence of employers raising wage offers to attract the scientists and engineers they want. But the evidence points in the other direction: Most studies report that real wages in many—but not all—science and engineering occupations have been flat or slow-growing, and unemployment as high or higher than in many comparably-skilled occupations.
The unemployment rate for recent STEM graduates including fields in which it is claimed there are shortages is quite high. Post-docs are increasing in duration, generally considered a sign of an inability of newly-minted PhDs to find any other job.
Why then do Bill Gates (net worth: $67 billion), Larry Ellison (net worth: $43 billion), Sergey Brin (net worth: $22.8 billion), and Mark Zuckerberg (net worth: $13.3 billion) feel the crushing need to import more foreign graduates? Because they want to push down the wages of the workers they employ. Simple as that. IMO there’s already a prima facie case that they colluded to prevent competing on wages with each other. Is it that much harder to believe that they’d lie to push the wages for their workers even farther down?