re: Same reason they didn't go back and re-image the "face" until it was extremely convenient, I would guess
(assuming you are talking about MGS imaging. Correct me if I'm wrong) There are a lot of spots on mars that have never been imaged at high-res at all. They tend to take priority over spots that we already have images of. I hope that they don't rearrage their schedules because you will scream "Conspiracy!" if they don't.
About your several false assertions:
NASA certainly does talk about Mars' radiation load.
It certainly is feasable to send astronauts to Mars, and we will do so.
Nobody with the wits to realize that "War of the Worlds" was fiction, believes that "Mars is Earth-like, and thus an "easy" place for man to migrate to." Certainly no one at NASA does.