The reason we can make medical diagnoses so efficient is because we have had the collective experience, and that the human body does not vary radically from one person to another such that it would be hard to keep track. While a doctor can’t be expected to know every intricacy of the human body, it has been catalogued and studied extensively over thousands of years, and this information has been made available for quick reference. Between experience and the rigorous education, doctors will know a significant amount of detail such that they can diagnose (or confidently know how to delegate this) fairly quickly. It’s not perfect, of course, and you are right that sometimes the symptoms are fixed rather than the causes.
Compare, however, to software: unlike the human body which has numerous small variations but a common base, software is free to take many different forms and frameworks. This software continues to change over time, so while documentation certainly can exist, it can be immensely fragmented and describe complex behaviours. Plus, when software developers fix an issue it often tends to stay fixed; there is a use for a postmortem but no immediate necessity. But in people, this has to be diagnosed every time it is encountered, so it is natural that documentation will occur.
(This isn’t the perfect metaphor, of course, but I hope it roughly corresponds.)
Compare, however, to software: unlike the human body which has numerous small variations but a common base, software is free to take many different forms and frameworks. This software continues to change over time, so while documentation certainly can exist, it can be immensely fragmented and describe complex behaviours. Plus, when software developers fix an issue it often tends to stay fixed; there is a use for a postmortem but no immediate necessity. But in people, this has to be diagnosed every time it is encountered, so it is natural that documentation will occur.
(This isn’t the perfect metaphor, of course, but I hope it roughly corresponds.)