David Easton is one of the most prominent scholars who focuses on systems theory in political science. The objective of Easton’s work, based on the experience of the natural sciences, was to devise a systematic model that could be applied to the whole field of political science. Although the author’s contribution to the development of systematic studies in social and political science is unquestionable, Easton’s model has not been adopted in the conduct of empirical research. The main objective of the article is to explore the reasons why political scientists do not use Easton’s model.