You may recognize the title as the 10th Agile Principle. The exact wording is actually, "Simplicity--the art of maximizing the amount of work not done--is essential."
It sounds straightforward but so many people have a hard time with this principle. Why?
-Some managers may not want to be accused of avoiding work. They don't want the slight appearance of having a cushy job. Maybe they fear it won't look good on their next performance review.
-Product Owners/Managers want as much business value as possible and there is nothing wrong with that. But they may fear that if they don't get all the features now, they never will.
Maximizing the amount of work not done, simply puts us in a better position to succeed. It forces people to think if they really need the feature their asking for. Furthermore, it allows Agile teams to work on the user stories that truly deliver business value. If a user story is deemed to be low value and high risk, ask yourself if it should even be in your backlog. Why would you have your team work on something that delivers very little value and is highly risky? Surely there is more important work the team can tackle.
@allenholub says it best, we should avoid everything that adds complexity.