They show all the time for me when the "Scene area" (what I call the "Stage") has been resized to be smaller than the Scene size. Also, if there are elements placed outside the visible Stage area, the scroll bars are displayed. There are no Preferences (or other) settings that I know of that influence this behavior. (I'm using "Hype Pro", but I do not think that would be different from "Hype" standard, in case You are using that version.)
When I have an element selected, the viewer centers on that element, can I disable this feature?
Not aware of any settings the user can adjust in this regard.