You need diverse product supply. You need diverse expertise. You need ongoing service. Very seldom can one provider give you all that. So you have to outsource, often with multiple vendors. That’s where good vendor relations management becomes important.
Having multiple vendors involved in service delivery requires co-ordination, diplomacy, accountability, and ongoing negotiation.
There can be conflict or gaps in service delivery.
Leadership and collaboration is required to assemble a team of suppliers who can deliver component projects that integrate with the big picture project.