u/SmolGeologist

Because naval units cannot travel over deep ocean until cartography, the geography of any particular game can easily bottle up my navy and limit the amount of good it can do. Protecting settlers/trade and helping to promote overseas colonization/expansion? Can't really do that until cartography. Waging war against a far away overseas competitor? Can't do that until cartography. Circumnavigation? Cartography. When naval units are restricted to coastal waters only, they can quickly become stuck and unable to reach any new islands/continents or even any rival players