And yet there are plenty of companies that openly exploit the visa system to bring cheap labor. Just check the top companies with the most H1Bs and you'll see a lot of consulting firms.
I forget which H1B consulting farm it was that emailed me(a citizen), but they were advertising a "Full-time salary job" doing software engineering in NYC, $39k/year.
Yea...no shit they won't get any takers and will use that as evidence to hire H1Bs.