You could actually make a case that carriers might even have a financial disincentive to update their phones. Some users might be more likely to update to a new phone if their old phone still has older software. That is precisely what Apple does to their users. They upgrade older phones with some of the newer features, but if you want everything, you have to buy a new phone. Many people say that the iPhone 4 could handle all of the new features of the iPhone 4s (including Siri) but Apple doesn't it give it to older phones so that you'll buy a new phone.