REST (or, rather, how REST is broadly used) encourages you to think in terms of Resources rather than Models or ViewModels. At first, your Resources start out as mirroring Models. But a single Model rarely has enough data for a screen, so you develop ad-hoc conventions for nesting Models in a Resource. However, including all the relevant Models (e.g. all Likes of a Post) is often impossible or impractical, so you start adding ViewModel-ish fields like friendLikes to your Resources.
Full article