The Product Owner role was created to address challenges that (development) Teams had with multiple, conflicting directions, or no direction at all with respect to what to build. This single source of “the need, in priority order” keeps the Team focused and reduces churn which is the result of waiting for answers, or conflicting priorities.
Without a Product Owner organizations often have a number of problems:
All priorities are consider “No 1” which, as a Team member cannot work on more than one thing at a time, results in the Team member choosing the top priority
Team members (developers) don’t have a clear understanding of what is the most important thing to work on and make the decision to work on something based on their perception of the priorities which may or may not be correct.
Interruptions to the work happens as stakeholders (managers, support, etc.) go directly to Team members to get their issue addressed
Teams do not appear to meet commitments they have made, as the interruptions and lack of priority result in work churn
Throughput of value delivered decreases while the time it takes to deliver an individual item (cycle time) increases on average reducing the effectiveness and efficiency of the Team