For off planet research: because ( https://xkcd.com/695/ aside ) we don't care if the robots "die". Human space exploration has an enormous amount of overhead to keeping the humans alive at all; even the sensors humans bring with them are compromised by having to be operable in a spacesuit.
Not saying that there isn't value to sending humans into space - it's just that that value isn't in gathering data for science, other than on the astronaut-subjects themselves.
If they are so much better, why does anyone get up off their couch and do field research? Just let the robots do it.
Besides, it's human nature to explore, in person. As George Mallory said, "Because it's there."