it's rude to spend someone else's money without their consent
Josephine is on a school field trip to NYC, and her mother gave her a credit card to use for emergencies only.
Josephine wants to purchase souvenirs with her mother's credit card.
Josephine calls her mom to ask if it is okay that she buys some souvenirs.
Josephine goes on a shopping spree with her mom's card.
Josephine's mom sets a strict budget, but allows her to use the card for souvenirs.
Josephine's mom goes to use the card back home, and it is declined.