Why?
If you have to ask "Why?" I don't think I would be able to explain it to you. But I'll give it a try anyway.
The short version: Let's put industries and pollution in orbit, where God intended.
The long-term version: Every time there was a frontier the best and brightest (as well as the misfits) headed that way, resulting in a better population in the new areas and a poorer one in the old areas. "The cowards never started -- and the weak died along the way." Look at it as a "frontier filter."
The human race needs frontiers.