Answer:
Countries specialize in order to increase their trade. Imagine a country that has specialized in rubber production and suddenly other more efficient synthetic products have replaced rubber. That means that the demand of rubber has fallen. This would create the country to face labor unemployment, lack of trade for rubber, a long period of stagnant growth indirectly effecting the economy adversely.
Therefore countries prefer to go along with trade and avoid specialization so as to avoid period of stagnant growth.