Created datum planes/axis should have size relative to screen. This will make it easyer to find a plane/axis that you need in swarm of others.
When you are making plane/axis on a small area of part you are usualy zoomed on it, so making datum relative to screen at that point makes sence. Creating plane as offset to part face should create plane with size relative to face.
This can be config option to turn on/off this option and define size ratio to screen.
Personal work example: Imagine aircraft sheetmetal part bent in 2 directions with 100`s of rivet holes and each rivet hole needs plane and axis to define hole. Creating these datums and selecting right ones is nightmare because you need to resize evry datum to avoid clutter.