alt Hacker NewsFriction of paperwork. Not saying it's right, but it's a reason.
Also, you are shifting the blame for immigrants getting arrested to the owners. That means the employees are actually blameless: they are caught between seldom-enforced laws and a need to thrive and feed their families.
Yes, again, I don't personally blame the employees. I think the vast majority of people who unlawfully immigrate to the US mean well. There's actually pretty broad agreement on that, despite the psychopaths running enforcement right now; CBP is still paying bonuses for voluntary departure.