The good thing about space is that you don't have to worry about the native people.
Jokes aside, you are right, of course. We don't have to worry about environmental effects or native populations in the same way when dealing with off-World colonies on sterile worlds. That alone should provide some incentive for commercial exploitation of things like asteroids; at some point Earth will either run out of certain elements, or other factors will result in certain elements being more easily obtainable off-world.