From my personal experience and observation, a large amount of employers that say that they can't fill their open positions, skilled or unskilled, have unrealistically high standards. They would rather leave a position unfilled than risk making a bad hiring decision. To give them a benefit of doubt, they might have more to loose from a bad hire than a successful one.

Of course, I don't have any direct experience with the few companies that are famous for pushing the boundaries of the H-1B visa.