At some point you do need some separation between watched bindings and pure logic, that's what the services are for. And quite often people are going to violate

At some point you do need some separation between watched bindings and pure logic, that's what the services are for. And quite often people are going to violate those principles of separation until they find out it's a really bad idea. However the fact that it can be done wrong and get someone into trouble doesn't change the fact that data-binding between the controller and the view is also very useful.