Think tvOS, for example. There have been rumors going on that we are going to see improved features for the iPad ... in a future release. We're expecting them shortly after the release, maybe a 10.1 release. The initial release is going to do very little for the iPads. This is, most likely, because of time. They need to focus on the thing they consider to be more important, and for now the fact that it releases with the new iPhone means that the phone gets priority. iPad features get to take a back seat. Imagine, though, if we had an iPad OS. They'd have to hire more people on, most likely, but it would be for the best. We wouldn't have to think "hey, will Apple be focusing on the iPad this time around", because they would always have a team of people whose only job was to make the iPad shine.