Simplicity is, simply put, the lack of complexity.
In the modern world, complexity is looked upon as a sign of advancement and prowess. Simplicity is viewed as the earmark of an amateur.
Fortunately for Lean companies, this is not true. It is much harder to accomplish something with simplicity than with complicated overkill.
Why is this fortunate? Because complexity costs money, both initially, for maintenance, and in the confusion it creates. The more companies that follow the myth that complexity is better than simplicity, the fewer companies there will be that compete with the truly Lean companies.
Granted, sometimes a complex problem requires a complex solution, but don’t go there first. Shoot for simplicity in any process you design. Use visual controls to make it even simpler. The fewer moving parts a process has, the less chance there is to make a mistake.