Ordinarily, say if someone were putting together a piece of furniture, their logic would be much more astute, if something looks too loose they would say "oops, that's not right", accepting their mistake without a second thought. So why are people so irrational otherwise?

The school system teaches people that reality is the ultimate test and to look for errors in yourself when you make a mistake, it then teaches people to view authority figures in the same way, to them their teachers, and future employers, are as infallible as reality itself. Thus they grow dependent on external validation processes, either reality or authority, and when they need to rely on their own validation processes their logic is far more flawed.