Facts you already know: Part proliferation and complexity affects almost all departments in a company. Still, processes are optimized department by department. Pronounced departmental thinking prevents an active inter-departmental collaboration and can result in a failed company-wide project.
In most cases, the vicious circle of part proliferation starts in Engineering and Design; sometime it also starts in the sales department caused by customer-specific requirements that led to variants and specialized products. During the marketing phase of the new product, the departments Purchasing" and Material Handling are already engaged in purchasing or storing parts or components. At the same time, the departments Process Planning, Process Control and Production start production and assembling of drawing parts and components. Finally, there is the after-sales-service department that has to handle the designed part as a spare part for a very long time after production finished.
In each department, there is a large potential to save costs resulting from reduction of part proliferation and avoidance of useless re-invention of existing parts. The latter can be achieve only with the help of the design department.