I know of two reasons.
1. The "blue states" have, quite deliberately, stopped building housing. This closes a traditional way out of rural poverty, and I think/speculate it's a major driver behind the opioid crisis.
2. The book "Dignity" by Chris Arnade documents the life of dirt poor America. I strongly recommend it. It talks a lot about how many people belong somewhere, and won't move because of that.
Regardless, people without those skills exist. Us HN people never meet them, and have a hard time imagining their lives, but they're still out there.
I completely agree that our educational system is fucked and needs to be fixed. I don't see how that would help the people who already went through the fucked up version, even if it ever got fixed, which I think we can agree isn't likely the next decade at least?
To learn about how the "permanent underclass" lives, You could do worse than reading "Dignity": https://www.amazon.com/Dignity-Seeking-Respect-Back-America/...
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