Whilst it probably won't be any Optimus robots doing that sort of job, he does have a point about using automated systems to do the mining and extraction of minerals in places that humans are ill equipped to work in. Of course the best places to do that are actually off planet, some of the asteroids are believed to be very rich in various forms of metal. If humanity is going to colonise our solar system, it will be the robot probes finding and extracting the minerals first that gets us there!