"And it's nobody else's responsability but their own. And no, they are not "careless". They are just human."
Responsibility comes from conciously following procedures and otherwise doing the best job you can in the way you've been taught. As you say we're all human and make mistakes, but that's not necessarily through being irresponsible.
If a responsible person makes an honest mistake that causes a catastrophy, then it would be far more productive to investigate why the procedures in place didn't prevent the accident. Punishing the individual does nothing to help stop the same thing happening again.
The increasing culture of the blame game is extremely unproductive.