One thing that leads to those faulty promises, IME, is that we often conflate estimates with commitments. When you work in a scrum team with a well-established

One thing that leads to those faulty promises, IME, is that we often conflate estimates with commitments. When you work in a scrum team with a well-established workflow, and you have the experience that we usually finish around 20 story points per sprint, then shouldn't commit to finishing the next sprint with 20 story points. You also know that that effort and technical challenges etc. vary greatly, so you can only do a commitment to, say, 8 story points per sprint with a straight face. And now, try to tell somebody why you only commit to "so little" work being done by the end of the sprint when you tend to get much more work done... Mostly impossible, in my experience.