At least from my experience (I used to be a consultant) consulting jobs mostly attract people that can't get a job elsewhere. They generally include low pay, long hours, and a lot of client interaction.

It's no surprise to me that the nation's biggest software consultancies are largely considered the worst places to work as a software developer.

H1B's know to apply at these jobs because they have a much better chance of getting them. They have a better chance of getting them because these same companies are generally the ones abusing the system to hire software developers below market rates.