Having buildings is definitely not a prerequisite for mapping addresses (when I go mapping I will typically and them before too, but again that is only a minor

Having buildings is definitely not a prerequisite for mapping addresses (when I go mapping I will typically and them before too, but again that is only a minor amount of time compared to actually gathering the data). Mass mapping buildings is a rather recent phenomenon in OpenStreetMap and you can have a high quality, fully functional map with not a single building outline (as google shows too). Not to mention that we have had a country with full address coverage since ages that only has a small number of buildings mapped (DK). Now there are certain high detail tasks for which having building outlines make sense: for example adding entrances with addresses, but that is fairly far along on the path of iteratively adding more detail to OSM.