From today's modern society, that's true.
But from history's perspective, we realize currencies took in many forms...including the most bizarre ones.
German Crisis Money Around 1921
Chinese Kuan note is the world’s oldest known banknote, from around 1380
Bank notes from Belarus
Katanga crosses used in Zaire, Africa
Wooden bills of Germany
Rai Stone, On the island of Yap in the Solomon Islands
Zambia coins in honour of the 2000 Sydney Olympics
The world's largest note
The death penalty dollar
Canadian Tire money
Bank of Cthulhu
Space Quid, currency to be used in space
The African nation of Zaire