Southern Pacific Switching Layout

[Justinmiller171]

I just thought of something: How come on ISLs all of the cars on the train are either pick-ups or set-outs on the layout, don't locals switch multiple industrial parks each day?

This would make it prototypical to have cars on your train that don't belong on your layout since they have been picked up or are destined to be set-out "beyond the basement"