What's the fun of exploration if you don't go there yourself? You can send a machine out to conduct mineral surveys but you can't send one out to create diplomatic relations to other cultures. And taking a picture of a planet is not the same as the visceral experience of going there and becoming immersed in its culture.
Sending starships to explore space isn't the same as 'Taking' it. At least, not if you did it the way Star Trek does it, I guess if you did it the way real humans do it, it would be 'Taking' it.
If your goal is best combat performance you'd probably want humans doing the strategic decision making and robots doing the aiming.