Most, but not all, "REST" APIs (other than the web) violate at least one element of the definition of REST, most commonly they don't actually implement HATEOAS, requiring out of band knowledge of applicable resource URIs or URI patterns and/or information about data formats not communicated by documentation of media types and hypertext relations.

But that's because REST is often used as a buzzword by people who don't know what the architectural style entails, or aspirationally to describe one goal of the design of an API, but one that may be compromised for conflicting goals.