It feels weird to argue against suburbs while I'm living there, but...
Most pro-density/pro-mass-transit people aren't arguing against rural lifestyle. They're against suburban, car-dominated lifestyle.
I'll conjecture that, for many people, the potential benefit of living "close to nature" is more than negated by driving everywhere. Commuting in a subway in a mega-city easily racks up thirty minutes of brisk walking per day.
Most pro-density/pro-mass-transit people aren't arguing against rural lifestyle. They're against suburban, car-dominated lifestyle.
I'll conjecture that, for many people, the potential benefit of living "close to nature" is more than negated by driving everywhere. Commuting in a subway in a mega-city easily racks up thirty minutes of brisk walking per day.