We've had a constant selection pressure for people who are economically and socially adaptable to move away from small towns since the start of the industrial revolution.
The issue is who is left in the towns. It's people who are socially and economically highly resistant to change.
What's interesting is why they are so resistant, studies show it's an overdeveloped sense of fear. They are terrified of moving to a new location. I know many people who refuse to visit any city because "it's too dangerous". People in small towns today live in a constant state of fear. Political and religious organizations have stoked that fear to a fever pitch.
Unsurprisingly, depression and anxiety rates are high in rural communities. Areas that also have poor mental health services. So they use drugs and alcohol at a higher as a form of self-medication.