Because before it existed, more than 3,000 years ago, humans relied on bartering to trade goods and services. Two dozen eggs for a sack of potatoes. Ten sacks of grain for a sheep. Transactions were slow, messy, and ineffective. As business picked up, they had to.
Certain easily identified goods, like animal skins, salt, and weapons, were introduced as a sort of currency; some standard medium of exchange. The unit values of this commodity money were still negotiable, but this transition eventually paved the road to metal money:
In 1,100 B.C., the Chinese, for convenience, moved from actual tools and weapons to miniature replicas cast in bronze. Those, in turn, proved prickly and dangerous. Thus, they were recast into a more convenient shape: a circle. They heralded the first coins.
Coin money was born in 600 B.C., in Lydia, now part of modern Turkey. The currency, the first in history, increased the empire’s trade and made it one of the richest and most powerful nations in the world.
And though paper money existed in China as early as the seventh century, it was not printed in Europe until 1661, in Sweden.
Increased international trade, the first currency market, currency wars, credit cards, mobile payments, and today,
virtual currencies and contactless payment wristbands. As for tomorrow, who knows.