Suburbs exist only because of government subsidies - they wouldn't be built in a free market because they are just too damn expensive. They require massive public funding for infrastructure - roads, water, sewage, side walks, etc, over the course of decades. At the same time, that infrastructure is only used by the residents of the suburb by design. They don't permit through traffic nor do they allow for mixed use. The problem isn't growth in a free market. The problem is just the opposite in fact.