I forget where it was, but I once saw a quote that essentially said that "a geologist on Mars with a hammer could learn more in one day than we've learned from every robotic mission we've sent, combined"
I think the basic truth in that statement is relatively easy to demonstrate. Each rover we send to Mars moves only a few tens of kilometers over its lifetime, and, though the science each one sends back is amazing, there's a limit to what we can learn without sending up some humans to do things in person. Robotic missions are limited to the exact configurations of their tools and where their propulsion can safely get them; humans are much more mobile and way better at improvising.
I think the basic truth in that statement is relatively easy to demonstrate. Each rover we send to Mars moves only a few tens of kilometers over its lifetime, and, though the science each one sends back is amazing, there's a limit to what we can learn without sending up some humans to do things in person. Robotic missions are limited to the exact configurations of their tools and where their propulsion can safely get them; humans are much more mobile and way better at improvising.