With respect to quality, I  see the key point of 5S as ruling out causes of problems. Let's say you encounter a quality problem in a clean, uncluttered workplace with accurate signage that everyone understands and abides by, You know right off the bat that it's not due to dirt and grime, clutter, or confusion. It narrows your search for the root cause. 

I believe Toyota uses 4S, not 5S. Also, the attempt to translate five Japanese words starting with S into five English words also starting with S was misguided as they are grossly inaccurate. Early on, I heard a more accurate translation in the UK for the first four S's: R.I.C.K., or "Remove, Identify, Clean, and Keep Clean." 

The meaning of the 4th and 5th S in the common English translation is completely lost. Seiketsu is about reducing the first 3 S's to daily practice through management enforcements, including procedures and audits. The 5th S, Shitsuke, is what you accomplish when the practices become second-nature in the organization. It's part of "the way we do things around here." When you train children to brush their teeth, you first have to remind them every day. That's Seiketsu. After some years, they do it on their own, without needing a reminder. You have reached Shitsuke. 

It's been over 30 years since 5S has been introduced in this country and, to this date, factories that practice it are the exception, not the rule. Many have attempted it and, in many factories, what you see is the vestiges of failed attempts. If anything, this legacy should tell us not to present it as simple and straightforward. That it is technically trivial does not make it easy to do. It's quite the opposite. It's all about human behavior, and it makes it difficult.