AngularJS - What's the point of mocking data via $httpBackend?

I just started writing my first unit tests in AngularJS via Jasmine.

Somehow I still do not understand why I should mock the $httpBackend. To make clear what's still unclear to me I will write down a small example:

Imagine I have a service (myService) that's getting data from an URL:

 function getData() {
    return $http.get("http://example.com/data")
       .then(function (response) {
          return response.data;
        });
 }

Let's assume that a GET call to the URL "http://example.com/data" returns following data:

{
    firstname: "John",
    lastname: "Doe"
}

The corresponding test would look like this:

describe("Service: myService", function () {

    beforeEach(module("myApp"));

    var myService, $httpBackend;

    beforeEach(inject(function (_myService_, _$httpBackend_) {
        myService = _myService_;
        $httpBackend = _$httpBackend_;
    }));

    afterEach(function () {
        $httpBackend.verifyNoOutstandingExpectation();
        $httpBackend.verifyNoOutstandingRequest();
    });

    it("should get data", function() {
        var mockData = {datakey: "datavalue"};
        $httpBackend.whenGET("http://example.com/data").respond(mockData);

        var promise = myService.getData();
        $httpBackend.flush();

        promise.then(function(response){
            expect(response).toEqual(mockData)
        });
    })
});

Unless I am mistaken, the test should pass, although the mocked data is not equal to the real data. The test would always pass, no matter how I set the mocked Data, because the service function would always be redirected to what's set in $httpBackend.whenGET("http://example.com/data").respond(mockData);.

I thought the purpose of such a test is to check if the returned data from a GET call [in this case myService.getData()] is REALLY the expected data and not some random mocked data. So whats the actual point of mocking data instead of checking if myService.getData returns the real data {firstname: "John", lastname: "Doe"}?

I'm well aware that I could also set the mocked Data to {firstname: "John", lastname: "Doe"}, but when the real data from the URL would be dynamic, the mocked Data and the real data wouldn't be equal again.

Thank you in advance!