Plus, off-shore outsourcing to India and other locations is growing rapidly. Any job done by someone sitting at a desk with a computer and a telephone is a candidate for off-shoring.
Middle-management prefers H1B's. Hire an H1B, and you have an individual working under your middle-management, under serf-like conditions. Do an off-shore outsource, and you have an entire work-function being done by outsiders under their own managers. You own company's middle-management will fight that every step of the way.