One of the most striking things I learned about the Rwandan genocide[1] was how many Tutsi simply refused to flee, even temporarily, even in the depths of the slaughter. Not because they wanted to make a stand or affirmatively resist, but seemingly out of some ineffable resistance to change. AFAICT, the same phenomenon has happened in every other genocide, not to mention other large scale disasters.

Economists can and should debate and quantitatively measure varying aspects of and reasons for the phenomenon. But from a high-level public policy perspective the reasons are largely irrelevant; there's simply no denying that on the whole most people by their nature are extremely averse to moving, even in the face of impending death. Any public policy predicated on intragenerational migration in response to run-of-the-mill structural economic dislocation is doomed to fail. Many people will follow straight-forward economic incentives. But a very large number won't, even to their extreme and readily foreseeable detriment. That makes failure inevitable.

[1] See "We Wish to Inform You That Tomorrow We Will Be Killed with Our Families" (https://en.wikipedia.org/wiki/We_Wish_to_Inform_You_That_Tom...)