Why is not updated scope in Angular JS?

This is because the callback function in your service is outside the angularjs digest cycle.

For tackling this, there are two ways:

Method 1:

The first way would be to use $scope.$apply just after your callback in the service has finished as follows:

appService.get({id : id}).then(function (response) {
   $scope.vm.events.push({title: 'New event', type: 'important', draggable: true,    resizable: true});
   $scope.$apply(); //this for updating your scope outside the digest cycle
})

Method 2:

Wrapping your service code inside a function inside the controller's scope as follows:

$scope.fn = function() {
    appService.get({id : id}).then(function (response) {
       $scope.vm.events.push({title: 'New event', type: 'important', draggable: true,    resizable: true});
    })
}

So, in this method, whenever you want to call the service just call this function. This is also the reason why your 'add' function updates the template because it is in the 'scope' of the controller and in the digest cycle.

If you are not seeing it, it is because the promise is not being resolved.

Do try putting something in the rejection handling part of the promise (on a second function within the 'then()' block):

appService.get({id : id}).then(function (response) {
   $scope.vm.events.push({title: 'New event', type: 'important', draggable: true, resizable: true});
},
function(){
 $scope.vm.events.push({title: 'ERROR_EVENT', type: 'ERROR_CALLBACK', draggable: true, resizable: true});
});

Like others suggested, if this is outside of angular, please call for $scope.$apply() or $scope.$digest() to trigger a digest cycle so that your data can be updated.

By adding this second function you should be able to see if the promise was being resolved or not, and if the problem lies elsewhere.