The problem is that outside of a few tech hubs, most companies are unwilling to pay developers salaries that even come close to what they can make in a tech hub. So the best developers move to the tech hubs, where the jobs tend to be more interesting and pay better. Plenty of people would take a 25% pay cut to live in a cheaper city than SF, but the reality is that they might have to take a pay cut of 50% or more, and even when you adjust for cost of living, that sort of pay difference is still dramatic (housing might be cheaper in many cities, but car ownership, healthcare, groceries and your kids' college tuition are largely the same).