Credit cards are unsecured debts. There is no collateral that can be repossessed to cover the credit card debt. Therefore, they are high risk loans for the credit card issuers. High risk = high interest rates. Also, lenders can charge whatever the market will bear. If too high, not even the rich people will apply for their cards.
The advantage of a good score is for low risk, collateralized loans (mortgages, car loans, etc).