Why should I use link type "Tracks/Contributes To" instead of "Parent/Child" for Cross Project Plans?

This is a well known scenario: Project Area A has the plan Items (Backlog Items), which are linked to execution items (Tasks and Defects) in Project Area B. Project Area A is owned by the Business, who will create and track backlog items. Project Area B is owned by Development, who will break down the backlog items into tasks and defects as needed.

My question is: why should I use the "Tracks/Contributes To" relationship between plan items and execution items instead of the "Parent/Child" relationship?

I know that both relationship types can be used across different project areas. I also know that the "Parent/Child" relationship does not require the project areas to be associated, plus the plan item is shown in the plan.

Are there any other reasons why I should use "Tracks/Contributes To"?

Thanks!!