Hello Frédéric, it is true that one can send commands remotely to spacecrafts/rovers. The problem though lies in the vast distances. Because light travels at a finite speed, there is a time lag between sending and receiving something. Even for nearby objects like Mars, this time lag is in the order of minutes so one can’t control a robot in real-time which is critical for some remote operations.
I have a feeling I wasn’t clear in the post that I meant remote-control of machines in near-real time. Sorry!