In her foreword of Graphic Design Theory: Readings From The Field, Ellen Lupton notes the importance of taking a step back to reflect on work:
With so much to do, stopping to think about why we pursue these endeavors requires a momentary halt in the frenetic flight plan of professional development. Design programs around the world have recognized the need for such critical reflection, and countless designers and students are hungry for it.
(Ellen Lupton, “Foreword: Why Theory?” in Graphic Design Theory: Readings From The Field, 2009)
“Why?’ when the professional already knows “How?”
Theory is a guide, an invitation to consider the world differently.
Theory is also a “critical” necessity as design is no longer a technical question (Can we do it?), but rather an ethical one (Should we do it?).