Por que se surpreendem?

Este resultado, "Queda de 20% nas casas para arrendar" é uma consequência perfeitamente normal:

"Those of us who were trained by the great Jay Forrester at MIT have all absorbed one of his favorite stories. “People know intuitively where leverage points are,” he says. “Time after time I’ve done an analysis of a company, and I’ve figured out a leverage point — in inventory policy, maybe, or in the relationship between sales force and productive force, or in personnel policy. Then I’ve gone to the company and discovered that there’s already a lot of attention to that point. Everyone is trying very hard to push it IN THE WRONG DIRECTION!”
...
Another of Forrester’s classics was his urban dynamics study, published in 1969, which demonstrated that subsidized low-income housing is a leverage point. The less of it there is, the better off the city is — even the low-income folks in the city. This model came out at a time when national policy dictated massive low-income housing projects, and Forrester was derided. Now those projects are being torn down in city after city.
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Counterintuitive. That’s Forrester’s word to describe complex systems. Leverage points are not intuitive. Or if they are, we intuitively use them backward, systematically worsening whatever problems we are trying to solve."

Por que se surpreendem com as consequências perfeitamente normais dos sistemas em que intervêm?

Trechos retirados de "Leverage Points: Places to Intervene in a System"