I not quite understand for what, need HUD class? For what it can be used?
It has a bunch of unique functionality. Have a look at the override list. Most importantly, Hud Draw → lines, boxes, text, it can handle mouse collision, it is more performant than widgets but offers little flexibility. Folks still use it as a hub for widget communication since it’s a singleton.
It saw heavy use before UMG was a thing. If you can believe such thing.