I presume more complex experiments on site, that take time and gave a lot of steps and decisions to be taken. of course this also can be automated, and probably at lower cost overall minus potential casualties, but then there is irrational/emotional aspect to getting to a different planet, which is perceived as major milestone in mankind's aspirations.

mountaineers also go to potentially deadly situations voluntarily, just because the those peaks "are there". nobody gets satisfied enough from someone's else photos and says "nah, that's enough of an experience for me", albeit view doesn't offer much more. Neither they do send drones up there instead of them :) (btw that would be a nice use case for some remote high-adrenaline-vr gaming with androids!)