Lean Production, as an approach to managing complex operations, was introduced more than 30 years ago. Yet, despite decades of Lean thinking and practice, the utter dominance of its industry by Toyota (the inspiration for lean), and the well-documented gains by those enterprises that have practiced lean in a high fidelity fashion, Lean is often viewed as a shop-floor skilled trade, to be assigned to subject matter experts in staff (not line) roles; and conducted through programs and initiatives rather than as fundamental to the means and methods of the firm.
A key reason is that Lean in particular, and other methods of achieving outstanding operations more generally, are primarily taught as the practice of tools and techniques—and not as a complete, coherent system of thinking that addresses the strategic concerns of senior leadership.