Because there is a shortage of skilled STEM workers.
The mere possession of a degree is no guarantee of ability. I look for track record using the skills and ability to work well with the current team when interviewing a candidate. The ability to quickly master a new technology is also key. The CS field moves very fast. Business and industry are constantly pushing the next meme or fad. If you're not ready to embrace and exploit the opportunity, you lose.
I work - when I can find a job - in the Silicon Valley.
Your statement is complete B.S.
All native-born - and many naturalized - citizens that I know of in the chip design world are unemployed.
That is pure crap. There is no shortage.