People are stressed, get distracted, are tired, don't have complete knowledge etc. This is kind of like arguing that null pointers aren't a problem, you "just"

People are stressed, get distracted, are tired, don't have complete knowledge etc. This is kind of like arguing that null pointers aren't a problem, you "just" have to check all usage of the pointer if you make it null. In practice we know solutions like this don't work