Because we can not control uncertainty and the variation it can bring, we try to take it out of our decisions. This is futile. Uncertainty is a part of reality.
The point at which we stop collecting information to make a decision is the point where we accept uncertainty.
"What interests me is the question of how humans learn to live with uncertainty. Before the scientific revolution determinism was a strong ideal. Religion brought about a denial of uncertainty, and many people knew that their kin or their race was exactly the one that God had favored. They also thought they were entitled to get rid of competing ideas and the people that propagated them. How does a society change from this condition into one in which we understand that there is this fundamental uncertainty? How do we avoid the illusion of certainty to produce the understanding that everything, whether it be a medical test or deciding on the best cure for a particular kind of cancer, has a fundamental element of uncertainty?"
--SMART HEURISTICS: GERD GIGERENZER Link