If you think about it, money is weird, and we seek to make it invisible. I've heard rumors that in the basements of the Federal Reserve, the Bank of England and others, there are cages full of gold bars belonging to particular countries, and as currency fluctuates or transactions are enacted, forklifts shuttle the bars from one cage to another.
We consumers carry paper cash, a bunch of scrips, so we don't have to learn to drive forklifts. And our use of the paper is continually decreasing, as we switch to little plastic cards or tapping out keystrokes on Amazon. We see physical representations of money less and less.Postage stamps are another funny little scrip that may soon become extinct. Sweden and Denmark are about to launch Text Messaging Postage (capitals mine, not the official title) whereby when you want to mail a letter, you text the postal service, they deduct money from an account of yours, and text you back a numeric code. You write the code on your envelope where the stamp would normally go, then drop the letter in the box.
As an irrelevant aside, while I was looking into this in a Swedish-language newspaper, I saw they have this little ever-changing box on the paper's website:
Maybe we should put one of those on this site....