Plate imaging, digital postpress, binding and finishing. Printers send you the step they cannot run in-house.
You are matched on these by name and on how far the work has to travel. Take a service off your catalogue and you stop being sent that work the same day.
Somebody wanting 500 visiting cards never reaches you — that pass is skipped outright rather than filtered afterwards. Neither does a press breakdown; engineering enquiries go to the service experts.