Predictions are always difficult - especially about the future ― Niels Bohr
― Neandertal's Guide to Cost Estimating, Naval Aviation Systems
This is a quote often used by those conjecturing that estimating is a waste. The quote is true of course. Making predictions about the future is difficult. But that has nothing to do with the need for predictions and the estimates that support them. When making decisions in the presence of uncertainty about some outcome in the future - this is the basis of Microeconomics of decision making.