Is U. S. currency backed by gold or anything else? Why do people work hard to get it?

U. S currency is not backed by gold or anything valuable commodity. In other words, it is as many other countries' currency, a fiat money; that is, money that is worthy because the government of a country realizes them as their legal tender.

The reason why people work hard to get it goes beyond any physical guarantee or commitment by governments or any big corporations, organisations on the value of USD. Instead, it is the belief of the people that USD will maintain its role as a storing-value tools, that is, its purchasing power will be kept at certain level over time.

Such belief is built on the strong ability of the USA to keep itself as the world's leading countries in term of economy, political, science and technology. As a result, the belief that USD will be the most popular and most-trusted currency in the world, as it has been for many decades.