What’s great about those asteroid landings is that they are relatively easy and nevertheless exciting enough. Much more exciting than the ISS or anything happening in low earth orbit. I think that’s the most important purpose of manned spaceflight. Robots will be able to tell you pretty much everything about geology, water and the potential of life on Mars.
A robot cannot stand on the tallest volcano of the solar system and tell you how it felt.
Robots can tell a lot, but not everything. Exploring is not only knowing what's there, but actually experiencing it in human terms. The richness of the reports from astronauts on the Moon cannot be approached by what a robot can tell you. Also, a robot can only answer the questions it was designed to answer and, thus, it embodies, in its own construction, a series of assumptions about its target environment that may be completely off.
The goal is to put humans on Mars (and every other place). We must focus on what we need to learn to make that happen. Asteroids and the Moon seem good steps in that direction.
