In the case of Columbia, even if someone had seen the insulation strike in real-time, they would've had to make an abort decision based on very limited information within a matter of seconds. From all accounts that I've read of the Columbia launch, nothing shown by the cameras or by the telemetry indicated there was an immediate problem. An abort is itself very dangerous, so a rush to abort could just as easily cause an accident as prevent one.

In satellite operations, our motto was "make haste slowly." You can't be as deliberate during a launch because things happen much faster, but you still have to make an informed decision.