The Azure Notification Hubs (used by Mobile Services) are (I think) unique because they wrap the complexity of communicating with the three major notifications services from Apple, Google and Windows. You can send the one notification to the service and have it distributed, at massive scale, to all three. If you wanted to write and maintain that infrastructure yourself, you’d spend lots of your time keeping up wit what’s changed and making fixes. The beauty of having someone else (in this case, Microsoft) do all that is that you can get on with writing your unique application, and leave the common stuff to someone else.
(I’m wearing my TechEd 2013 shirt today and it says “only write the code that only you can write”)