Suppose your friends, Mary and John, received their first credit cards with identical features. Mary uses her card extensively to make purchases, always paying the full balance in a timely manner so that she incurs no interest cost. John pays for everything in cash, reserving the credit card only for an emergency that never happened.

After two years, your friends apply for a new credit card.

Explain why Mary is offered a new card at a much lower interest rate than John, despite of the fact that they have similar jobs and make the same amount of money.