Agile implementations, and Scrum in particular, created these roles for a reason; they are there to address specific problems that arise from more traditional approaches to delivering value:

• Scrum Master: Coach the agile team to high performance
• Product Owner: Single source of the priority of what we need to work on

So while these roles have a number of other responsibilities, agile implementations leverage these roles so that the team can delivery as a group far more of the right stuff than if they would operating as a set of individuals without those roles.

The team literally operates at a level that is more than the sum of the parts.

Traditional approaches assume the unit of production is the person. Agile approaches assume the unit of production is the team. The problem is that in order to become high performing you need to focus on the interactions between the people, not just the individuals themselves.

In other words you need a coach for the team, someone who takes responsibility for how the team is working together, helps protect the team from outside influences, helps the team address things that are getting in the way of their work, and generally support the team in their day to day activities.

This is the role of the Scrum Master.

Traditional approaches focused on the implementation of multiple projects where people were assigned to projects. The capacity of each individual was typically sliced so that X% was to be used by project X and Y% was to be used by project Y, and so on.

Problems arise when the portion of the allocation is used, but the output required by the project is not delivered. What does the person do? Work more on one project over another? Talk to their manager to determine priorities? The manager might also be the source of a third set of work (“our VP wants us to work on this now!”) as might peers of the person (“could you just help me out on this?”).

The result is that it was often left up to the individual to make the decision on what the most important item is. These decisions are made in isolation from others, from the projects, and from the business.

We need a way to get control of the work and to determine what the most important thing is that the team can be worked on.

This is the role of the Product Owner.