People may know the best decision and not make it: study
Well, there's the old 'exploit-vs-explore' tradeoff, and it's well known in decision theory that without perfect information (and in real life, there's never perfect information) it's not optimal to always take the 'best' decision according to currently known information, sometimes you should take a potentially worse choice just to gain information about how good that other alternative is.The multi-armed bandit problem (https://en.wikipedia.org/wiki/Multi-armed_bandit) is a theoretical simplification of this concept.