Again: it keeps the dataflow simple, no business logic is hardcoded and IT can concentrate on constructing the dataflow. While the business expert is defining the business logic.
Because is business logic is referenced by the dataflow - and not implemented in the flow - when the business logic changes, the dataflow does not have to be changed.
Have a look here:
https://youtu.be/oe4r6DCDxC8
Carpe Diem