Flying cars are uncommon not because they are dangerous, but because it requires a huge amount of energy to defeat gravity in addition to propelling the vehicle forward.
Cities are more populous and wealthy than ever before because there is no substitute for human proximity in a service economy, and more humans in close proximity makes for more productive services.
Cities are more populous and wealthy than ever before because there is no substitute for human proximity in a service economy, and more humans in close proximity makes for more productive services.