Why is required to create a WIP order to control both internal and external repair flows?

Integration between WRP and external repair execution is going to create automatically a work order in WIP module.

And also, when creating internal repair order in Depot Repair module, it can be generated a work order.

Which is the business need to have this work order? Or should be considered as a functionality required by the architecture of Oracle Applications, where no user iteraction will be required?

Regards.