To reduce cycles of rejection and redesign -- especially in the absence of clear acceptance criteria and the diversity of possible development paths -- User-Centered Design (UCD) has become a central methodology in computer science, emphasizing the integration of user perspectives throughout the entire system lifecycle. Despite its widespread adoption, however, UCD remains conceptually ambiguous and theoretically underdeveloped. This paper addresses that gap by drawing on the theories of Ernesto Laclau and Jacques Lacan to analyze UCD as a potential empty signifier: a term that gains rhetorical power precisely through its semantic openness. We argue that this ambiguity enables UCD to unify diverse and sometimes conflicting expectations under a shared label, which both empowers participatory design practices and conceals underlying tensions. Acknowledging UCD as an empty signifier allows for a more critical engagement with its practical and symbolic functions, revealing how it can foster inclusivity, empathy, and user empowerment, but also how it risks ideological capture and conceptual dilution. This theoretical reframing opens new pathways for reflection and renewal within sociotechnical system design.