SQL has 'interoperability' re: an ANSI standard. Theoretically you should be able to get off all those old Oracle contracts right? Eventually there are little nuanced things that users end up building their workflow completely around. Even if you change no functionality and just slightly alter the GUI, you're going to have complaints that something is broken. Inertia is your #1 vendor lock in feature. EPIC is as golden as Oracle just due to resident incumbency.
#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).
While I strongly agree with points 2 and 3, SQL standards are useless when hospitals invent their own schemas and data governance. Looking for serum creatinine? Good luck without local knowledge. There are probably 30 tables (not exaggerating) for that lab, and the closest you can get without chasing 7 people for info is grepping all the table names for "/CREA/".*
#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).