Exactly. I checked the bit about Australia after I mentioned it yesterday, and it was actually Visa that blocked DCC transactions an their network. They claimed it was to protect customers. They were brought to court, and paid a hefty fine. The regulator decided they were only protecting their own income by blocking DCC.The opposite, the issuer loses out on FX margin/fee opportunity, so it's in their interest for you not to use DCC.
My own view is DCC should be banned