Easier to fire? Still costs less? Do what they’re told, because they’re chained to the company and job?

Because H1b is an arrangement that more or less amounts to indentured servitude where vulnerable people have their visa status glued to their at-will employment agreement, resulting in a dynamic where employers can and frequently do expect unpaid overtime, fewer sick days, and otherwise disproportionately greater value from h1b employees, and those who fail to meet these unfair expectations are let go and effectively evicted from the country as it is extraordinarily rare to to secure another h1b job within 60 days.

The number on two paystubs can be the exact same while one person is being brutally overworked and the other given a leisurely, comfortable WLB, which effectively amounts to underpaying the foreign labor, per unit of output, devaluing each unit of labor of domestic output.

Because their H1B status is tied to their job so they will put up with way more abuse.