Project Manager and/or Scrum Master

The roles of Scrum Master and Project Manager continue to be discussed in the blogsphere, with most commentators clearly distinguishing between the two roles and indicting they are not compatiable, and not suited to be combined.

Steve Hunton blogged on the Scrumalliance website that A Scrum Master Is Not a Project Manager by Another Name he says:

Contrary to popular belief, the ScrumMaster and project manager roles are highly different and shouldn't be confused. As more companies migrate their project management to Agile, many do so without a proper understanding of what they're aiming for. In particular, there are incorrect assumptions made about the roles in Agile; people often expect that the shift from Waterfall practices includes a wholesale shift of roles. The ScrumMaster, however, does not play the part of the traditional project manager.

He goes on to say:

Traditionally, the project manager is a leader, a decision maker, a planner, someone who manages the project and the team and is the person accountable to the business for accomplishing the project objectives. The ScrumMaster's role is more that of coach and facilitator, a role that sits between the project and the customer. The ScrumMaster doesn't manage the team that produces the work; instead, he supports the product owner, coaches the team, and makes sure that Scrum processes are adhered to. The ScrumMaster is responsible for the Scrum process, its correct and continuous implementation, and the maximization of its benefits.

The PM Stack Exchange has a series of answers to the question "Why can't the scrum master and the project manager be the same person?"

 Scrum makes the distinction between supporting the team in WHAT work they do and HOW they do it. Trying to have one person play both of these would create a great deal of conflict. How do you choose in a stressful situation between negotiating features or helping the team grow and reach consensus. A scrum master is a facilitator, how can he/she facilitate if she owns the project too?

Erin Beierwaltes provides the following graphic to distinguish between the various roles:

(Click on the image to enlarge it)

Despite the advice and general acceptance that the roles are not compatiable many recruiters and employers continue to advertise for the combined role - why should that be?