Thats because you can't afford to feed a family on what an H1B visa holder gets paid.
I know with some of the Asians imported by the financial sector here in the NYC metro area the salaries are probably 75% of the Americans’ wages - but they are forced to work 150% of the hours. Trafficking these coolies isn’t just to suppress wages; it is also an end-run around hard-fought labor reforms that gave Americans nights and weekends off.
Along the NY/NJ border were iron mining communities where in the 19th century people slaved away six and a half days per week (Sunday afternoons were off) for little more than room and board; when the mines closed the workers fled with what they could carry because many were in debt to the “company store”. We are returning to those dark days; workers live in housing they will never own, driving cars they lease, and when they die the next worker will move right into their apartment and vehicle. There will be nothing to pass along, which is acceptable to some because there are no heirs anyway. At least the iron miners could raise families...