#2 is the whole risk aversion thing. Any platform migration is going to have political risk attached to it. Nike won't move away from Oracle even if Postgres can do everything it can line for line because paying the $200k maintenance fee each quarter is a cheap recurring cost compared to the political risk of a failed project.
That's not even factoring in #3, the little features here and there which are value-adds to the platform and not part of the standard. I've inherited projects where my firm offers to support O&M for some poorly written ASP 1.1 Classic software. We'll go in, patch some business-logic bug, and get a phone-call later that afternoon asking to rollback our fix. Turns out their users had integrated bugs into their workflow such that when the software operates "properly" (i.e. 'to spec') it actually breaks things (i.e. stops operating in an expected fashion).
*Based on a true story.
My point was that the model you describe is dated and broken. When consumers have the choice to make decisions around technology, price and value, they'll do exactly that. Right now they have no say in the matter, as you've pointed out.
The EHR model will eventually lose because its one sided. Consumers and patients are completely left out of the picture and EHRs have no incentives right now to change. Beyond that companies like Epic are operating on outdated business models. The days of the black box of data that lives inside the four walls of the health system are numbered.
Consumers won't deal with a dumpster fire of technology once they have the choice. Digital health will win once the barriers of compliance and interoperability are broken down.