One good reason for the doctrine of stare decisis is that if judges know that their decision will bind future judges, they have an incentive to develop good rules, rather than just rules that favor a party to a particular case who may be sympathetic. If a good person driving negligently runs into someone loathsome who was not negligent at the time, rule-of-law notions require that the good person pay. It’s very hard for some people to accept that; stare decisis encourages judges to do it. Unfortunately, stare decisis in the US, and especially in the Supreme Court, is pretty much dead.
I think this idea somewhat resembles what I see as the best reason for tenure for academics: it forces those who decide whether to keep someone on to look at the merits more carefully than they might if the issue were only “shall we keep this person (whom we like, and who has cute children) on the payroll for another year even though he hasn’t written anything very good.” Academics not on the tenure track seem to have even more job security than those who have to go through tenure review.
“Why didn’t various governments create and publish a plan for what they would do in the event of various forms of financial collapse, before it actually happened?”
Same reason the money that was supposed to go to flood control in New Orleans got spent on more-visible projects. What politicians do is get elected, not solve people’s problems. How would devoting energy to this sort of plan win votes? The sort of person who would even consider this sort of thing wouldn’t be running for office and wouldn’t get campaign contributions if they did.