"More than 80% of the workers working across three assembly lines were contract employees paid minimum wage for eight-hour workday...when their shift ended, many walked off the job, he said—even if the lines were still running." Of course they did, that's what anyone in that situation would do surely? Are they supposed to work for below minimum wage because the company can't organise shift changeover properly?
No -- well, it depends, and that's a false dichotomy. I work until the job is done (or I'm cut) and the workplace is safe. It's the employer's responsibility to pay me at least the legal minimum wage for hours worked. If that means I'm going into OT because they can't organize shift changes properly, that's their problem. There are usually also legal or contractual requirements for breaks, so I'd be prepared to say "…
If I'm a minimum-wage contract worker, I might have another job to go to after this one and I can't work OT. I need to go home, feed my children perhaps, and then get them to bed before my night shift at Food Co. or my evening English lessons.
If you're paying minimum wage, and not hiring your workers full time, you can't automatically expect your hires to just "stick around" for overtime.
Also, many employers do not let employees take overtime period because in some places once a contractor passes over XX hours per week, they are entitled to benefits.