Why? Why can't we develop better robots? To me we could be exploring better technology and send that into space instead. Let people get their thrills bungie jumping or something else.
Because robots can't do squat. Talk to some people who do robotics for a living. (There's a big group at CMU.) Just as an example, a robot designed to do simple retrieval can't tell the difference between a tuft of grass and a rock. I suppose we could build one to waive its arms and say "Danger Will Robinson" but that's about it.