There's probably some stickiness and deception in exploitative workplaces. From the outside they may seem better ("Make $X per hour! Guaranteed hours!"), but once you quit your existing job, move away from home, and work at the factory long enough to realize you were happier before, you may have lost the opportunity to go back to your old life -- your job may be gone, the cost of moving may be too high, you may not be able to take the reputation hit for returning home a failure.

But yeah, you are correct. There are many shitty, hazardous, dangerous, health-destroying, depressing jobs paying next to nothing out there, where it is a rational decision for many people to work there, their best option. And if the companies involved had to make the jobs not suck, they'd probably be better off automating away most of the jobs. Or more realistically, moving to a country which was willing to let the shitty jobs persist, because hey, jobs.

But "better than subsistence farming" shouldn't be the bar we're trying to clear in the 21st century.