Exactly because the consumers of those API's exhibit a strong preference for one or the other.
Library/module/API developers often seek to deliver maximimum adaptibility in their interfaces so that consumers of them can satisfy their own more specific/pressing requirements.
We've used it. It's useful to define the contract between teams.
So you have 2 teams do a meeting, we work out a contract we like, dump that into a jsonschema and you can enforce by unit tests that schema is respected on each side (producer/consumer)
I've seen OpenAPI/Swagger in the wild a few times. It's a good way to specify the API for an HTTP server, whether it's JSON or something else. Biggest downside is the confusing name change.
