Competitive Labor Markets
Let us not forget that many of the IT giants claiming that there is a shortage of qualified US IT workers are the same companies that illegally colluded to reduce or eliminate competition in the labor market by agreeing not to "poach" either other's talent, thus suppressing wages that would normally be bid up by those firms to attract talent. There is NO shortage of domestic IT talent. It's just that, as with so much else, IT firms are in a race to the bottom in terms of wages and benefits.
I do not blame the people getting H1-Bs for anything. I have found them to be eager and hardworking and focused on building a life for themselves here in the US, and I agree that getting a green card should be easier. I have also seen how the whole H1-B process is like formalized indentured servititude, where the company that "owns" your H1-B visa controls your destiny, and usually suppresses your earnings as well until you qualify for a green card.