Why use it? Why are we bound to use it? Is it a law? If so from who, God or man? Why can't OUR planet be free for all to enjoy? Just simple child-like questions.
When I was a child, money was a rare thing around my community. It was usually a median that we received for the crops at the end of the year, and used to buy gasoline and fertilizer for the next year, and the things necessary to keep the farm running. My mother bought the groceries that we didn't grow by trading eggs with the grocery store. He traded the eggs with a supplier to restock the store. Every year the excess from the garden was given to some families close by who didn't have enough to eat. In short we used money, barter, and charity to provide for our family and the community. Today the source of money has changed, barter is rare, and charity lives on.
Now, to answer your last question. The farm I lived on growing up produced enough food to feed about 20 people. Today it produces enough to feed 20,000. If it were not for the thing you call money, there would be a lot more hungry people in this world.
Why use it? Compare the US to much of Africa.
Are we bound to use it? No
Is it the law? No The US Monetary System provides a standard currency system to allow for easier trade, but you are free to make your own as long as it is not passed as currency of the US Monetary System.
The scriptures are not about your type of money, they address only how you spend it.
Finally, why don't you enjoy it now? Psalms 118:24 This is the day which God hath made; We will rejoice and be glad in it.