It isn't a lack of incentive to move it is a lack of ability. Think about what it realistically costs to move to NYC right now, first months rent, last months rent, deposit, and even then most rentals aren't even on the market unless you pay a broker several thousand. The majority of people in rural america surveys can't handle a 400 dollar emergency let alone the cost to move to a large metro.

And before you say "well they can get the money to attempt a move by selling their family property", realise what you are saying. Sell dilapidated rural property to whom exactly? How does that happen?

Unless you have grants of approx 15-30k to bring people to cities I don't think it is even possible. And what cities would even want this to happen enough to participate? Probably places like Cleveland? Detroit? Out of the frying pan into the fire I suppose.