What you write sounds good, and you seem to have the experience to back yourself up, but the overall picture doesn't make sense:
You say that people who stop doing this back-breaking, underpaid work end up better off. If that's the case, why are people still staying on the shitty job? Why aren't they making what looks like a no-brainer decision from our viewpoint?
As I said in the original comment, there are many possible reasons. They have already moved from their farm to live in a slum in the city, and can't go back. They probably owe some money for that move, maybe even they owe money to the mine. They maybe even live in mine-supplied housing.
Of course, the lure of "lots of money" is a strong one, and they will work for years and years thinking one day they will have the lucky break that will make the difference and pull them out of poverty. (side note: sound familiar? Look around you)
Like I said, read grapes of wrath to see an excellent account of how people head towards this "working dream" only to become disgustingly trapped working as slave labor, continually going backwards even though they work harder and harder. When they are unable they are kicked out to die and replaced.
And finally, many people do quit and attempt to get away from it all, but there is an endless stream of naive newcomers to continually staff the mine. (again, see this clearly shown in grapes of wrath)
You say that people who stop doing this back-breaking, underpaid work end up better off. If that's the case, why are people still staying on the shitty job? Why aren't they making what looks like a no-brainer decision from our viewpoint?