That investment is absolutely worthwhile, but we aren't even vaguely close to a general-purpose robot that can do what humans do. One human geologist could do the work of an entire fleet of Curiosity rovers. It's a matter of if all of the associated dangers of space travel worth all of that scientific knowledge gained from both sending people to do interplanetary science and from developing new tech to get us there is worth it - IMO, the answer is a resounding 'yes'.