Businesses are concentrated in city centers because that's where the people (i.e. potential employees) are. Even better, there is a robust market for both employees and employers, meaning people are not stuck in an area where only one company exists and everyone living in a 20 miles radius is not either a coworker or someone working a service industry job that gets half of its revenue from people working at your one available office employer. I don't think it would do much for ones quality of life to have to move every time one changes jobs.