They have a monopoly over letters and your mailbox. See: https://www.cato.org/tax-budget-bulletin/privatizing-us-postal-service#:~:text=USPS%20Advantages,postal

They have a monopoly over letters and your mailbox. See: https://www.cato.org/tax-budget-bulletin/privatizing-us-postal-service#:~:text=USPS%20Advantages,postal%20systems%20in%20the%20world https://www.cato.org/tax-budget-bulletin/privatizing-us-post....