So why does all this end up being the case? I think firstly it derives from wanting to flatten history into something that's just too simplified. Categories like civilisations and empires and realms often do a lot of historiographical work, and visualisations like this present them as consistently *the same type* of entity, even if some are city-state collections and not unified polities at all. There is no one model of what a "civilisation" is and political power overlaps a lot in reality.