The decision makers have a very, very strong incentive to keep things going. And the PR circus surrounding the teachers made it worse in the Challenger case. Meanwhile, everyone else has a strong incentive to shut the hell up.
Besides, saying the engineers didn't "try hard enough" is essentially claiming the engineers were in charge. They were not. Managers are paid to manage their department, not just please the higher ups. When a claim is made that failure to address a problem will result in catastrophe and loss of life... really what more needs to be said, or drawn, to make the point? If you're not going to trust your own experts, why have them at all?
And how does the Challenger explosion in any way suggest that there aren't enough engineers? Certainly this one major issue had engineers urging for delay, so there doesn't seem to have been a lack of them.
You know that all of the shuttles risks are well documented, right? It's a mountain of issues that basically gets the "ok to be ignored for now" stamp at every launch.
Besides, saying the engineers didn't "try hard enough" is essentially claiming the engineers were in charge. They were not. Managers are paid to manage their department, not just please the higher ups. When a claim is made that failure to address a problem will result in catastrophe and loss of life... really what more needs to be said, or drawn, to make the point? If you're not going to trust your own experts, why have them at all?