It just didn't work well enough. People do die. In business, no one is expected to die, and the precautions taken are far more extensive as a result. Impregnability is a foolish desire. A continually decreasing breakdown is what is achievable.
People dying puts an upper bound on the worst thing that can happen.
It puts a limit on what you can do. An interesting perspective, to say the least. Impregnability is impossible because we can't perfectly model the future behavior of a large system. Hell, we can't even model a medium-sized one particularly well. The double blind relationship is the exact abstraction of the commodity relationship.