See link to blog below. But I can answer this question with one word, greed.
And contary to the report’s opinion, they do promote and put H1-B workers into advance position.
And what irratates me to no end, is that most of the recruiting companines for contract programmers seem to have fallen into the hands of folks from India. Add to that the fact they do not pay these workers the prevailing wages like the law dictates, and you have another screwing of the American worker.
Why high-tech firms bring in foreigners — Link removed