Because human beings are remarkably capable, especially the best and the brightest. There's a great paper called the "dispelling the myth of robotic efficiency." https://academic.oup.com/astrogeo/article-abstract/53/2/2.22... // https://lasp.colorado.edu/mop/files/2019/08/RobotMyth.pdf

Yes, a robot car that drives on its own will be a better driver than most humans who text and drive, or have 400ms reaction times.

But making a machine that can beat a 110ms reaction time human with 2SD+ IQ, and the ability to override the ground controllers with human curiosity is much harder. Humans have high dexterity, are extremely capable of switching roles fast, are surprisingly efficient, and force us to return back home.

So in terms of total science return, one Apollo mission did more for lunar science and discovery than 53 years of robots on the surface and in orbit.