[donzog]

EDI is standardized; however, the standard is not enforceable. So it's not like you can't send crappy data or some custom flavor of the format.

The problem is that the receiver of this "standardized" data has to work with it, although it often doesn't comply with the standard.

It's pretty much offloading all pain/responsibility to the other side. But you can do that with a web API, too - send a bad JSON over.

The only difference between working around the formatting issues, EDI or JSON, is the tooling. Developer toolkits for API are far more modern and advanced and have a higher pool of developers to choose from.