I mean they kinda do since lots and lots of systems support HL7 which can best be described as "JSON but so so so much worse" or "CSV with '|' kinda."
FHIR is an actually-JSON (+XML) health data protocol that is gaining adoption (most recently because of CMS Interoperability and Patient Access Final Rule), so it's not all bad.
:/
That being said, it is JSON but much worse