As part of the Scrum framework, the team conducts a Daily Scrum (I would not say a "meeting") lasting about 15 minutes or less, at the same time and place without fail. This is for the entire duration of the sprint. The prime objective of the Daily Scrum is to set the context for the work that the product team is taking on and to identify any impediments or issues requiring resolution. These are, in turn, taken note of by the ScrumMaster and the product owner, who work together to remove these impediments.
The cardinal rule for the Daily Scrum is that all team members are required to attend, and, according to Scrum definitions, both the ScrumMaster and product owner are committed team members and are expected to attend and participate. While there are many reasons why the product owner's presence and participation are vital, here are the top five:
Reason #1: Constant evaluation of business value
The development team's focus may tend to become too technical without the product owner's in-depth business knowledge and continual participation. Without this key component, the team's concentration may rest only on technical issues, while other relevant issues become lost in the shuffle. Before long, it is too late to realize what business value was to be achieved, and it's too late in the sprint cycle to turn around and recover that business value -- which is key to Agile principles. Therefore, daily evaluation of business value being generated through daily builds is critical and keeps the team, and the results it produces, on track.
Reason #2: Conflict avoidance/Keeping the team on the same page
Once the skill sets of every team member have been identified, the Daily Scrum provides for the most effective assignment of resources with those skills in mind. Though the product owner does not hold an overtly technical role, he or she is an essential team member. As such, he or she helps clarify and communicate key business issues and helps ensure that the entire team is in sync and tackles any problematic or difficult issues it might face, such as conflicts, misunderstandings, and awkward situations.
Reason #3: Self-organization (everyone in check and in place)
The product owner's participation in the Daily Scrum ensures that the team's self-organization habits are put in check and in place. Each member is expected to come prepared and to provide the status of the previous day's tasks, determine what they are expected to do today, and what, if any, impediments they are encountering. This helps in maintaining the team's focus throughout the sprint cycle and ensures that the team is on task and that development progresses smoothly throughout the cycle.
Reason #4: Clear communication across the board
When the product owner is missing in action from the Daily Scrum and a lot of work has taken place without his or her awareness and input, extra legwork is needed to bring the product owner in sync with the team or, worse, to realize that the team has progressed in an entirely different direction. As an example, I have observed teams going back one sprint in order to bring the product owner up to speed and catch up to them. This essentially defeats the Scrum principles on how the team should be operating. There could be many reasons for the product owner to be left behind, and keeping his or her day job is one of the biggest and most common. But the time commitment is only 15 minutes or less, which is essentially the same amount of time spent fetching cup of java from the break room. When you weigh that against the much larger amount of time lost by not attending, it's easy to see how crucial and beneficial the product owner's daily participation actually is.
Reason #5: Yes, it's tech talk -- but it's essential for business
Granted, sometimes the Daily Scrum's core discussion can be pretty technical, but it is still essential to the business, and it's worthwhile to share in what the team is actually discussing, building, and developing. Even if the business owner may not have any input for that day's Scrum, he or she (and the whole company) can still benefit greatly from simply listening to what the team is working through. This is also tremendously beneficial as far as shaping the right structure of the product being developed, and it keeps the morale of the team high, since no backtracking is required and everyone has a clear vision of what is expected of each team member and of the team as a whole.
I'm hoping that these top five reasons will help guide new product owners (and experienced ones). Daily Scrums set the tone for the entire sprint and help the team understand its own progress and reach success along with the product owner, ensuring that the sprint goes smoothly for the entire project.