I can think of $5 trillion reasons...
"Metalliferous asteroids as potential sources of precious metals"
"Successful recovery of 400,000 tons or more of precious metals contained in the smallest and least rich of these metallic NEAs could yield products worth $5.1 trillion (US) at recent market prices."
You guys have more faith in Private Indistry going into space than I do, but it’s a nice dream. We will see how it works out.