A small street is a lively place for a penny. It moves around so quickly between the hands of the people who need it. They need it to come so they can see it go.
Now, to these penny-people, dollars are frightening. Dollars are not comfortable in homes that touch neighboring homes. Dollars require green spacing between their home and the neighbors.
So, while dollars become stale in poorly ventilated boxes, pennies float like breath through crowded streets and homes, inhaled and exhaled by children who do not wait for the next penny but for the next full breath of air that fills their lungs.