Part of this may have to do that OpenOffice is more enterprise-oriented, so maybe more likely to be recommended by IT people with exposure to it, and more likely to be used in an organizational context. I actually recently searched for "openoffice" when I meant "libreoffice" (which I switched to years ago). So definitely inertia in various manifestations. I think this is why some forked projects make little effort to maintain "mental continuity" (visual, naming) with their parent; it might be just as well to appear as something entirely distinct from the beginning.