There's reasonable evidence [0] that the director of NASA and ground crews knew the Columbia's wing damage was bad enough to make re-entry impossible. But they had two options, tell the astronauts they were never coming home at the start of their mission, or wait until they discovered it minutes before their vehicle disintegrated.
The director chose the former path, and ended up getting fired as it looked like a cover up. It was really just being compassionate.
No pad abort system would have saved Columbia. But on the flip-side, while everyone is up and arms over the loss, NASA's astronauts are trained to WANT to fly. We can hem and haw and say what a tragedy, but there is a class of people who know the risks, who know the possibility of death always exists and will still pilot or crew the vehicles that we send into space.