This really isn’t as easy as it sounds. Moving means you lose your support system of friends and family etc. Some people have children and need the grandparents to help watch them during the day as just one example. Job opportunities are likely not the same. While their current city job may not pay a lot the opportunities from that job could lead a lot higher but of course life choices can be a gamble. On top of all of that, moving long distance is difficult and expensive.
I have a highly intelligent friend from a small southern town and he moved out of there because he recognized there weren’t any opportunities for someone with talent but no capital. Sure he could have stayed and bought a cheaper house but he’d still struggle to make the payment on his small salary.