Hear me out on this one, but Siri makes more sense on the iPad than the iPhone. While Siri is meant to allow hands-free input, in real world usage then people are constantly looking at their commands in order to confirm they were properly understood. So if inputting an appointment or search results in immediately looking at the device then wouldn't it fit better on a tablet where you are already looking at the screen, rather than on a phone where you are probably multitasking and trying NOT to look at the phone screen? I'm not saying it shouldn't be on iPhones because I use Siri regularly for simple tasks and I do believe it will be a standard input on all future Apple products. But, I'm just saying that if given a choice then I'd probably use Siri more on my iPad than on my phone.