The parent's description matches exactly what I know from people on H1Bs in the fashion industry, whose labor market conditions have some parallels with tech. I

The parent's description matches exactly what I know from people on H1Bs in the fashion industry, whose labor market conditions have some parallels with tech. I don't think it's limited to outsourcing companies. Long hours, death march deadlines, and generally higher-than-average salaries result in high turnover in fashion as they do in tech. Employers turn to H1Bs to lock-in a workforce, as, excepting large companies, few will expend the extra time and money (legal services and filing fees) to transfer a visa when they can simply hire away an employee from a competitor. The lack of labor mobility with the H1B is a boon to industries that would rather not reform the working conditions or improve the salaries that causes top talent to move around.