Making a different card size is foolish. Because all post machine sizes are the same. Perhaps, if contactless transactions become widespread, the size of the card no longer matters. Or the card doesn't matter.
But in today's conditions credit card sizes are like this.
Credit cards were first used in the United States.
But the conditions of the period prevented the spread of these cards. The use of credit cards similar to the present day began in the 1950s.
Having more than your monthly earnings on your credit card limit means you go bankrupt at the end of the day.
Trusting willpower in matters such as credit cards is not the right decision. There is no such thing as willpower. It is always a more efficient solution to restrict conditions as they should be.