Why do economists go to the extremes and work in marginally for an answer, give an example.

The correct answer to this open question is the following.

Economists go to extremes and work marginally for an answer because economics is not an exact science. It is a social science and the scientific method can't be used to make predictions.  

Economics is based on the social behavior and decisions of human beings. So economists cannot make rational decisions because the market cannot be predicted. It depends on many factors. Economists are able to forecast, based on variables presented in the moment of the forecast. But these are never considered predictions.

For example, the stock market. It is based on the manipulation of markets or the economic situation of a company. Supply and demand is another factor. So economists are limited in their capacity to make solid statements.

b) brahmans   is nomadic society