I think one of the reasons that the RPC model still dominates many people's thinking is that we really haven't gone beyond the HTTP binding defined in the first SOAP spec.
Agreed. Recently I observed two phenomena that might well be the main reasons the RPC model dominates: First, many of the people working on Web services standards bodies come from an OMG standards background. Second, many companies building Web service platforms (including some major vendors) view SOAP as just another wire protocol under their platform's existing programming model. Very few platform vendors have internalized service-oriented architectures and the Web services potential.