Elimination of waste is the number one principle in lean manufacturing and lean software development. Essentially, lean focusses on adding value and reducing everything else which does not contribute to create value.
Consultants produce a considerable amount of rubbish. No doubt. And consultants waste a lot of time / money on things which do not create value. Think about all the powerpoints and tons of slide decks, see rule #61: Create value. Not powerpoints. Think about all these endless workshops with an endless number of attendees and with endless discussions. Think about all these status meetings where people mainly report on activities instead of outcomes. Think about all the project plans with a detailed WBS which are outdated before even finished. Think about all the analysis reports written where the biggest parts of the document describe the background, history, methodology, generic explanations such as “SOA for dummies” or “Big Data is the new oil”. But concrete findings, recommandations or outcomes for the client are poorly handled. Or think about all these never ending “CC” or “Reply All” email conversations.
Many things which do not add any value. So, think lean and #63: Eliminate waste.