"Whatever reason" is because the quality of life in an urban area is much higher than in a rural "cheap" area. Jobs are centered in urban areas, you can eliminate a huge commute by living close to work, clawing back hours of your life. For those who are unable to afford a car the rich transit options available in urban areas are life lines to school, work, a community. Cheaper areas can be massive voids where go to the grocery store or post office is a 30 minutes round trip car ride.