Even if the carriers wanted to update users to the latest Android OS many devices come with a preinstalled custom UI and existing apps. You don’t want to mess w

Even if the carriers wanted to update users to the latest Android OS many devices come with a preinstalled custom UI and existing apps. You don’t want to mess with the users’ experience by changing their UI or what apps they expect to see. It would actually require a great deal of work to get new OS updates into the many varieties of Android phones in the way users are accustomed to their phones’ experience.