Team estimates and team commitments are foundational to reliable delivery
We all want reliability
Every leader I've had the chance to interact with wants to be able to accurately predict when some deliverable will be ready and then be able to deliver it on time. This is true in software development, hardware development, home improvements or even our child's school play. We all want this but we differ on how to bring it about.
Let the team estimate their own work
Estimates done by the people closest to the work are usually the most reliable. It amazes me that I'll often find someone in middle management estimating work on the team's behalf. There are many ways this can result in less than desirable results. Often the nuances that make work complicated are best known be the people in the codebase with fresh build experience. Centralizing estimation with an architect or manager may result in an overly optimistic estimate as they might not be taking all the tactical nuances into effect. A further challenge with delegated estimates is that it deprives the team the opportunity to actually ask questions and brainstorm on the approach. In this situation the person doing the estimating has all the information and makes a design assumption based on their experience and knowledge alone. Allowing the team to be a part of the estimate, ask questions and develop an informed plan will result in a more realistic estimate as well as a better informed solution.
Let the team commit to their own work
Often I will see Product Owners, Project Managers or even Scrum Master's committing to work on a team's behalf. They essentially "sign the team up" for work and then later in sprint planning reveal what the team is on the hook to do. This undermine's a team's commitment to a large degree. Adults are far more committed to actually getting work done when they have a chance to say what they can and can't realistically do. Sometimes managers will ask me "if they say how much how will I know that they're not undercommitting so they can have more free time?" It's a common question. After coaching more than 300 teams I've always found the challenge is just the opposite. If a team is brought into an inspiring vision they will usually OVER commit because intrinsically they're motivated to get the product to market. It may take several sprints to convince them they actually can't do as much work as they want to and will really have to prioritize instead of continuing to take too much work into a sprint. Very rarely have I seen a functional team constantly sand bag their commitments. Once they commit to the work the organization has every right to expect that they actually finish that work. Teams know this and will usually do whatever it takes to deliver on the commitments they make, this results in a much more reliable commitment. Over time the conversation shifts completely from "why didn't we deliver this?" to "what is most valuable thing we need to deliver next".