There is a hypothesis out there that says that this phenomena, at least here in the US, may have been the result of an intentional conspiracy by parties that had a strong financial incentive to require millions of people to commute in vehicles over very long distances each day. Who would benefit? Oil companies and car manufacturers, primarily, though also suburban home builders and real estate speculators, road contractors, etc. Who helped promote the conversion, in this scenario? The preceding, in partnership with the government and mass media. There were legitimate "non-conspiratorial" reasons why someone might want to live in a suburb rather than a downtown urban area (such as White Flight or new married couples wanting to raise their kids in an area far away from the perceived dangers of city life, such as bums, gangs, "perversion", etc.) But at the same time, there were certain industries and companies that stood to gain very well financially if the whole suburb-highways-long-commute-and-back system took off.