explain why pennies are still in circulation in the US!
And why haven't 1 and 2 dollar bills been replaced by coins years ago ?
When you go to the US you realise they use $1 notes a lot. I mean a lot. The two notes you'll use almost exclusively are $1's and $20's. Which is a good thing as any Australian, English or European will find astounding as soon as they get to the US is that all the notes are exactly the same size and colour.
When I was in the US, I got into the habit of carrying around a wad of singles, around $20 worth as you'd use them almost everywhere. If I had to carry around 20 $1 Australian coins at 9 grams a coin, my wallet would be dragging my pants around my ankles.
A better question is, why haven't they introduced a $0.50 coin, having to put in 10 quarters into a parking meter is silly, as is carrying around a crapton of quarters.
Also whilst we're on the subject of coins, why is a dime (10 cents) smaller and lighter than a nickel (5 cents)