You can get away with structured formats only when everything is fully automated, which works for APIs, but anything that needs human review will almost always

You can get away with structured formats only when everything is fully automated, which works for APIs, but anything that needs human review will almost always be opened in Excel. That rules out anything fancy like JSON. Excel supports XML, but it think most people don’t know how to use that, and I suspect it would only be useful for simple tabular data — not complex structures. Many/most business processes are not 100% automated, so you just have to fall back on something that works with standard business tools (Excel).