We're certainly starting to see a gradual transition over to XML/JSON via FHIR, and I've even worked with a couple of vendors that are pushing RESTful web servi

We're certainly starting to see a gradual transition over to XML/JSON via FHIR, and I've even worked with a couple of vendors that are pushing RESTful web services as their preferred integration method, but agreed: there's absolutely massive inertia behind legacy HL7. Implementation costs for a primary EMR are in the millions and most ancillary systems still cost hundreds of thousands of dollars to put in place. There's a lot of financial incentive for healthcare organizations to keep using what "works", even if it is ugly as hell.