I'm glad you asked that question. The difference is that during the road to permanent residency, we have a whole regime of protections around the worker in this environment. It's a unionized environment.
If workers are alone, by themselves, with no unions involved, they are fully on their own, and it's not the way it would be for you or me being non-union. If I don't like my job, I can leave, but they're tied to the employer. They have no labour mobility. The employer has them by the jugular.