Countries in the proximity of other countries are more likely to have larger trade volumes between them, increasing the chances they hold each others currencies

Countries in the proximity of other countries are more likely to have larger trade volumes between them, increasing the chances they hold each others currencies in reserves and have incentives to use a common payment network. This is why geographic proximity is relevant even in a fully digital world. At least while a significant portion of trade consists of physical goods that have to be moved across borders.