Question is not why we do it in aviation, look at the incredible safety record that keeps getting better, but why this is not done in medicine and road transport.
I thought the reason why it doesn't happen in medicine is that the lawyers got there before the safety experts. It's creeping into aviation a bit, I've seen threads on here where pilot errors and dismissal seem go together. This will ultimately mean less reporting of things that rely on the crew to report if they get penalised for it.