Unit testing on an Angular app with Karma

So i'm quite new with test cases and I have a small questions (specific to my case).

I am currently developing an Angular app and started to do unit test with Karma (Mocha/Chai). The back end of this app is a node RESTful API. So basically, the app is a bunch of controllers and services making some basic CRUD operations.

On creation of a new user for example, I handle the verification in the html form using angular's form directives. In the server side, there is also a verification on the object received. So generally my functions on controllers are no more then things like:

create() {
  UserService.create(vm.newUser).then(callBackToDisplaySuccessOrErrorMessage); 
}

It will probably sounds silly, but i'm new in this domain (test cases) and i am a little bit confused, so my first question is:

since the http calls are mocked, what is the point to do unit testing in app such as mine ?

And my second question is :

how to unit test basic app like in my case in a proper way ?