A citizen is the back bone of a society. Due to a citizen, a state or even a country can develop. Of there were no citizens, there won't be development in the society. They all work together directly or indirectly for the betterment of the people.
More is the population of citizens, more is the improvement of the nation. For example, a citizen works in a hotel as waitrer, another citizen works as engineer, another works as a Leader, etc.
Thank you