Simplicity–the art of maximizing the amount of work not done–is essential. — Agile Principle #10
A simple development process is a lean, efficient process with no unnecessary work.
This principle is the most direct connection between the Agile Manifesto and lean thinking, which calls for the elimination of all “unnecessary waste” from processes, and the minimization of “necessary waste” that a process needs to run, but that does not directly add value. In software development, value is in the form of working software, and everything else is waste.
A Simple Process Has Less Waste