What works
In entity views the ability to “Hide > When Empty” is correctly available and working (even for Formula fields) in all of the following areas:
- 2-column mode sidebar area
- 2-column mode top/compact bar area
- 1-column mode top area
Issue
But, it is missing in the main area of both modes:
- 2-column mode left main area
- 1-column mode bottom area
Use cases
In my opinion the use cases are a superset of those of the currently working areas, because arguably hiding something (particularly a formula field) when empty in the main area which is the most visible area of the entity view, would reduce clutter and confusion as much as hiding it in the side and top bars, if not more.
Related but not identical topics:
#Reduce empty relation noise when sharing entity
#Hide field on entity view if not empty
#Restore Default HIDE-When-Empty Behavior (with Option to Instead Show-When-Empty) in Display of Collections in Entity View
#Hide field on entity view if not empty