Dutch Shell is famous for its "scenario thinking" approach to planning. Wise planning assesses a series of alternative futures and how a company should optimally respond to each alternative.
Perhaps the best example of the failure of current day economists to fail to consider alternative futures is the 2008 fiscal crisis. In his testimony before Congress, Alan Greenspan -- America's premier economist and the head of the Federal Reserve -- admitted that he did not see the possibility of a downturn in real estate prices coming. He totally ignored that alternative future -- despite the fact that all the signs of overinflated pricing, ridiculous granting of mortgages to unqualified lenders, and the manipulation of the financial market was occurring and should have been easily identified.
The reality of uncertainty makes it necessary to consider contingency plans for alternative futures . . . but "bounded rationality," or the failure to consider feasible options, is a typical phenomenon. Herbert Simon, the Nobel Prize winner, addresses that condition in his book, Administrative Behavior.