Scarcity is a central concept in economics. It is in fact part of the definition of economics. The scarcity of means and goods sets the boundaries of economic science.
For example, there is only so much wheat grown every year. Some people want bread and some would prefer beer. Only so much of a given good can be made because of the scarcity of wheat. How do we decide how much flour should be made for bread and beer? One way to solve this problem is a market system driven by supply and demand.