Ideas are easy. Reality is hard. Doctors and pilots are often too stressed out to perform properly, if you are working 20 hour days you're probably out of it at hour 16. Careless mistakes often happen because people are expected to be machines. Humans were not made to do any of this. We're apes that have in a few thousands years decided we rather be machines. Not really decided, more like been coerced into being machines. And we don't know how to shut the system which tells us these things, which are lies, off. Just because you can do something, doesn't mean that you should. Human beings don't understand this concept. Just because you can do something, and someone wants you to, you absolutely should is the current human way of looking at the world.
Even when there genuinely is accountability like drivers and pilots who pay for their mistakes with their lives, it doesn't stop them making careless mistakes. I seem to remember that pilot error is the cause of the majority of plane crashes. It certainly is for car crashes too.