oh i think that people do learn, everybody learns, it's just that some people are more like experimental physicists. let me explain:
In physics, there are mostly two branches: theoretical physics (which makes predictions and does mathematical calculations on paper) and experimental physics (which touches things with their hands, does experiments and observes the outcome). the same is true in politics:
Some people see a situation, think about it, do some guesswork and write articles, discuss with friends what would probably be the outcome if a certain policy is implemented, then decide whether it's a good idea to implement that policy or not. Other people, however, take the opposite approach: implement the policy first, then wait and watch what happens. That's the experimental approach: do things and figure out the hard way. That's exactly what happens in politics. people vote for austerity politics, and for a while it goes well, until suddenly it doesn't anymore. then people crash and society suffers, and people observe this and then conclude that these policies did in fact not work well. that's when they learn. after harm has been done, and they've experienced it themselves.