Where is the "model" in AngularJS? The answer to this question is:
AngularJS does not work with a real model but just with a view model. Therefore, it shouldn't be called an MVC framework, and neither an MVW nor an MV* framework, but rather a View-Model-Whatever (or VM*) framework.
In summary, the answer to this question is: because unlike the general concept of an object type or class, the general concept of an association, as defined by UML, does not have a direct computational counterpart, neither in common object-oriented (OO) programming languages, nor in SQL.