I think the mistake you’re making is thinking Apple cares about messaging. They don’t. They care about the iOS platform. Messages gives them a competitive advantage in that sector. Yes a competing messaging service might surpass it, in fact this has already happened in China with WeChat. This goes some way to level of the playing field with Android over there.

But putting Messages on Android would level the playing field as well. It might give them the dominant messaging platform, at least outside a China, but so what? There’s no reason for them to care about that. They’re not Facebook.