People moving to a city, and having more disposable income to put into the economy, is not a bad thing. Increased vehicle traffic is a bad thing. You want to i

People moving to a city, and having more disposable income to put into the economy, is not a bad thing. Increased vehicle traffic is a bad thing. You want to induce demand for other types of transportation. There is a finite amount of people willing to move to X city / a finite number of jobs for them to support themselves.