Raoul is right that there's a psychological benefit to a rescue mission
It's important to make the point that NASA isn't intimidated.
In the same way, a mission where a Shuttle was lost but somehow the crew was rescued would be perceived far more positively than a mission where both were lost, or even a mission where (somehow) a Shuttle was rescued (autoland?) but the crew was lost.
From a straight logical viewpoint, the Orbiters are far less expendable than the crew, which even the astronauts know, but we're talking psychology here.