It's because of what makes the future. Only two things make the future. For 5,000 years people have been acquiring more and more formal education. It's safe to predict that people will continue getting smarter. By definition, you can't forecast a discontinuity because it breaks a pattern.
Oil prices rise, and then suddenly fall.
The birth rate rises, then suddenly collapses. Discontinuities are the hackers of forecasting. If you fail to plan you plan to fail. Just because it's difficult to forecast doesn't mean you shouldn't try. Leaders are expected to see farther than followers.