Resources are not always in terms of material terms. Poor people with family, friends, associates, familiarity of a region, etc. stay there. What's a bit unique for American migration patterns in the past 60-ish years people have become less and less mobile for economic opportunities and the cultural shift has sometimes become more resentful toward those that feel betrayed by those leaving regions for better economic opportunities. In a lot of countries people are happy and even envious of those leaving their areas of origin. The underlying reasons for lack of mobility is another heatedly debated topic altogether but there's absolutely plenty of things the poor, particularly rural ones, absolutely have plenty to lose.
It's the poor who are often able to put those issues aside because they have so little status and wealth. They have nothing to lose.