This has also happened to manufacturing and coal mining to a certain extent. But, unlike agriculture, the demand for certain resources like coal is significantly less than it used to be, but people in the affected areas haven't been able to find work in other fields.
It takes money to move, and it's unlikely they have the financial resources to handle living in an area with a significantly higher cost of living, unless the job pays very well. Given the fact that public school graduation rates are relatively low where they live, it's unlikely they would be able to secure one of those high paying jobs if they don't have at least a high school diploma or GED.
