Just because some people like to repay in full doesn't mean that everyone will repay in full, and banks themselves can't judge who will repay in full without issuing cards. Anyway, a certain number of people in the total amount have to pay in installments. Without issuing cards, banks make nothing.
In addition, banks and some merchants engage in some promotional activities to attract cardholders to pay by installments, and official website will also cooperate with some brands to pay by installments.
In China, only consumption is allowed, and cash withdrawal is charged, but in some foreign countries, there is no charge and cash withdrawal can be made in full. This is mainly to make money. Therefore, domestic cards can not become real credit cards, but are called quasi-credit cards.