This is an important question- most of the costs of a credit card providers come from dealing with fraud and chargebacks. That's partially because, under US law, credit card companies have to eat fraudulent charges if they can't get the person or company that did the fraud to do so. (Funnily enough, this is one of two places where protections for average people in the US are significantly better than protections for average people in Europe).
But credit card companies can keep their costs low by making a business decision not to renew the accounts of frequent chargeback-ers or chargeback-ees (even if they never officially found those individuals at fault). If the government had to make a payment system for everyone and take on all responsibility for all fraud, that would create an incentive with massive second-order effects.