Sometimes human beings want to go to outer-space, or into a volcano, or all the way to the bottom of the sea.  The problem is that human beings are not particularly adapted to these environments, and without a lot of really intensive preparation and fancy gear, they will die spectacularly on arrival (if not before).  Robots designed to survive in these horrible places can go in our stead, and send back useful information about conditions there.  But it’s hard to create a robot that can survive adverse conditions and still respond to them like a human being …