"1. No limits on working time. Salaried employees end up volunteering for the company they work for after 40 hours. If they don't work this unpaid overtime, they will be subject to progressive discipline up to and including termination."
And termination often isn't a matter of just finding another job but having to go back to country of origin, where jobs are scarce to nonexistent. This makes the threat of termination a huge, career-threatening thing, which tends to promote servitude. Which makes the manager's job easier and is more beneficial to the company.
Essentially slave labor.
A company I worked for gradually replaced the entire division with H1b workers, and I witnessed first hand that these workers essentially lived in their cubicles, occupying them all hours of the day and night. This was expected of them, on pain of being sent home.
A simple change to the labor laws, limiting the number of hours a salaried employee can be expected to work to say, 50 hours, on pain of high penalties, (or something similar) might go far to cut the heart out of this H1b scam.