Why Have a Separate Project Management Methodology?

The methodology most organizations are referring to is some type of Systems Development Life Cycle (SDLC) with a bit of project management thrown in. The project management methodology should address the specific project management deliverables. This includes specific processes for project initiation, prioritization, project planning, status reporting, issue/decision/change management, quality management, risk management, etc. These fundamental elements of project management apply to virtually all projects. The same basic project management methodology should work whether one has been implementing a new customer application or if one has been managing an office move. What would be different is the "Product methodology" - the methodology one needs to use to deliver the product or outcome of the project.