Man power... Robots will force man out of jobs and cause poverty. Robots can't think rationally and are not sophisticated as man. Robots can only do limited tasks. A world with robots is just sad and impersonal.
Ok, we're a primitive space-faring species ( ok, we send out "probes".... LOL)...and look what we send out....mechanical machines, with primitive brains...not even biological. So, if we MET a space-going craft, it could have a robot, because a metall...
At the "state of the art" there are not such robots yet. May be you have seen microscopic robots in movies or TV but actually they don't exist in reality. You have to wait for one or two decades to see that.