> The core problem it addresses is client-server coupling. There are probably countless projects where a small change in a server’s URI structure required a coordinated (and often painful) deployment of multiple client applications. A HATEOAS-driven approach directly solves this by decoupling the client from the server’s namespace. This addresses the quality of evolvability.

Not sure I agree with this. All it does is move the coupling problem around. A client that doesn't understand where to find a URL in a document (or even which URL's are available for what purpose within that document) is just as bad as a client that assumes the wrong URL structure.

At some point, the client of an API needs to understand the semantics of what that API provides and how/where it provides those semantics. Moving it from a URL hierarchy to a document structure doesn't provide a huge amount of added value. (Particularly in a world where essentially all of the server API's are defined in terms of URL patterns routing to handlers. This is explicit hardcoded encouragement to think in a style in opposition to the HATEOAS philosophy.)

I also tend to think that the widespread migration of data formats from XML to JSON has worked against "Pure" REST/HATEOAS. XML had/has the benefit of a far richer type structure when compared to JSON. While JSON is easier to parse on a superficial level, doing things like identifying times, hyperlinks, etc. is more difficult due to the general lack of standardization of these things. JSON doesn't provide enough native and widespread representations of basic concepts needed for hypertext.

(This is one of those times I'd love some counterexamples. Aside from the original "present hypertext documents to humans via a browser" use case, I'd love to read more about examples of successful programmatic API's written in a purely HATEOAS style.)