That's because it's the unit of value that the article's reader is most likely familiar with. When you go on vacation you're most likely constantly converting p

That's because it's the unit of value that the article's reader is most likely familiar with. When you go on vacation you're most likely constantly converting prices in the local currency to the currency you're familiar with - that doesn't mean the local currency is worthless (if that's what you were implying). After I moved from UK to US, it was months before I stopped doing the mental arithmetic from USD to GBP.