While I understand the point about Siri, Gmail (of all the Google apps) seems like a terrible example of the same thing on the Android side (Maps and its incestuous relationship with Play Services might be a better fit). What does Gmail do that Microsoft's Outlook app couldn't do if Microsoft were willing to invest the effort? Maybe I'm missing a feature I don't use, but the best I can come up with is being bundled with the device, but even there if Microsoft struck a deal with, say, Verizon, I don't think there's much Google could do about it.