Problem: Some fields within an entity may need different permissions than others.
E.g., if a Task has a “Due Date” field, this ideally would not be editable by the Assignee - only by a “manager”. But the Assignee will have Editor permission for most everything else in the Task.
A hack might be to use a lookup to a Due Date field that exists elsewhere, but that complicates changing the Due Date for someone who does have permission.