Merchant server decrypts and verifies the Authorisation Response. The merchant server then sends an encrypted, signed Purchase Response to the cardholder computer. This process is very secure, due to the implicit distrust that it requires. No single point unquestioningly trusts another, and requires authentication to proceed. This provides total accountability for the merchant, the Payment Gateway, and the end consumer.
Businesses have to wear the consequences of any fraudulent transaction their system processes.
When this powerful monetary incentive is combined with companies such as Visa implementing additional financial penalties on businesses that do not implement secure procedures, it becomes a motivation too strong to ignore. E-business can not exist without good security. This is a reality of today's e-commerce environment, and all vendors must at least become aware of the implications of not securing their systems. Unhappy customers, litigation, and inevitably financial ruin are on the horizon for those that do not. If you work for or consult to an e-commerce business, ensure they understand the gravity of what could happen if they fail to secure the way they do business, and this type of solution may well be the one you suggest.