Limit of knowledge
Whosoever wishes to know about the world must learn about it in its particular details. Knowledge is not intelligence. In searching for the truth be ready for the unexpected. Change alone is unchanging. The same road goes both up and down. The beginning of a circle is also its end. Not I, but the world says it: all is one. And yet everything comes in season. ~ Heraclitus
The problem is the limit of knowledge. Because of the limit of knowledge, the decision-making needs to be decentralized. By approximating the decision gives you the best shot at arriving at the best decision. Only with trial and error, you can get closer to the optimal decision.