If you wanted to put the equivalent of $1 million or more in currency in a suitcase, what currencies might you use?
How many zeros can you fit on a currency note? Yugoslavia managed 11 zeros, but Zimbabwe went to 14 zeros. I don't know how many zeros Venezuela has on its currency these days.
Sometimes it takes three paper notes to buy a cup of coffee. Sometimes it takes two notes to buy a car.
There's even a quirky little classroom-friendly cartoon video appended to the article on "The History of Paper Money."