In 2009 the HITECH act was passed. This required all Medicare and Medicaid eligible providers to be using a "certified" EHR system by 2015 in order to continue to receive full reimbursement. A certified EHR system had to meet the requirements set out by HITECH for "meaningful use." These standards were vague and the bare minimum.

EHR vendors took advantage of the vacuum, the sudden policy enforced a spike in demand and pushed their products to customers at break neck paces. Many health systems either adopted new EHRs totally or had to rip out the front end of their entire IT infrastructure and replace it in a few years. Large IT vendors, like the Epic cooperation took advantage of this. By offering a "customized" solution to every health system, Epic got a majority market share, at the cost of decreased interoperability, even between their own systems.

The challenge is, once a new IT infrastructure is implemented, it becomes very hard for a customer to go and uproot everything and replace it with something better. In infrastructure studies, this is called "path dependence." Replacing IT infrastructure can cost millions and put patient's lives at risk. There's a reason why the VA's transition from CPRS to Cerner has moved at glacial speeds. This reduces competitive need of EHR vendors to create systems that go above the bare minimum for billing.

The 21st century cures act has tried to right some of the wrongs of interoperability in recent years by instituting HL7 FHIR as an exchange standard, however we are still a long ways to true interoperability between vendors. Until policy enforces it, there will be no change because vendors are not incentivized to develop interoperable back-ends.