What's "the problem" that you contributed to? That humans are social animals and that as a group they are stronger than the sum of the individuals? I supposed by not starting your own business outside of London to cater to people like you where you came from does contribute to there not being businesses outside of London. But I'm not sure why that matters. You're only beating yourself up for not doing that and for moving to London.
All else being equal, neither the workers nor the employer has the time to wait around existing in a place where they can't get work or find employees, respectively, waiting for the other to arrive. An empty night club is just as much fun as a loner hanging out at the Circle K: no one wants to go to an empty night club, and no one is going to open a night club in a location just because people loiter there. It's about momentum, there's nothing wrong with a positive feedback cycle. The self-reinforcing is the cause of the continued and sustained congregation, because it makes it easier, more flexible, and reduces risk for all parties. Being in metro areas (traditionally) creates significant buffer and reduces risk significantly for both the employee and employer in terms of availability of prospects.
That both sides of a transaction have realized it's efficient to meet at the (defacto) marketplace (metro areas) in order to successfully and easily transact business (being employed/employing people) isn't lamentable self-fulfilling; it's descriptive of the state of how people interact and that the true value of a network is the connections, not the nodes.