Goldstein presents a number of reasons for why it is important to have an artificial scarcity of goods.
One reason is that the scarcity of goods helps to further cement a hierarchy of social classes. "But this would provide only the economic and not the emotional basis for a hierarchical society." That reason works. If there is supposedly a scarcity of goods, then only the wealthy are likely to have the money and access to them. It creates a society of "have and have nots."
Another reason is that it helps to keep the prices inflated. That is basic economics at work. With a limited supply, the price of items is driven up. The demand for those items might be high, but because the supply is so low, a manufacturer can keep prices high. The DeBeers family diamond company does this. Diamonds are quite a common stone, but the available supply is severely limited, so the price is driven up.
A third reason for Goldstein's artificial scarcity is that it keeps the workers working. If the population believes that their current efforts are barely keeping up with demand, then they are likely to continue working to meet that demand. They see a purpose and a need for their work.
Goldstein's solution for how to create artificial scarcity is an interesting one. War. Continuous war. War allows for manufacturing procedures to be operating at 100% while at the same time consuming those goods at an equally alarming pace. The goods are either being used immediately or destroyed because of the "war."