As a company moves from insurgent to incumbent, and gets big and complex and involved in lots of different things, it tends to end up with lots of different objectives, tactics and strategies. At that point, trying to understand it from outside, it can be useful to think not about what it's trying to do but what it's afraid of. This company want to do lots of things, but what's the existential threat? What does it want not to happen? What scares it, late at night?
For Google, the fear is around reach. Google is a data company, and a machine learning company, and everything it does is about reach - reach to get data in so that it can understand everything better, and then reach so that it can serve that understanding out to the users. And so Android exists partly to enable the expansion of the mobile internet, but also, and more fundamentally, to ensure that no-one (meaning first Microsoft and later Apple) would be able to block Google from reaching those users, both to give them each results and to see what they are doing. Google is afraid of going blind.
For Apple, I'd suggest the fear is that the developers leave. This is what happened in the 90s and it was a key part of the company's near-death experience (and arguably Apple only survived because the web made the lack of Mac apps matter less as a reason to buy a computer). Once developers start leaving you're in a vicious circle that's very hard to reverse (this is where Windows Phone is now). Today the iOS ecosystem is smaller than Android in absolute users and downloads, but has 7-800m live device, which is three times the size of the PC install base in 1995, and twice as much app store revenue per user as Google Play. More importantly, perhaps, the users are highly concentrated in key locations - Chase isn't going to abandon its iPhone app because there are 500m Android users in China. So right now the ecosystem looks sustainable, but that could change. Developers can leave. That's Apple's existential fear.
This is a useful lens to apply to the announcements at WWDC and IO. Google, this year in particular, always seems happier and more comfortable talking about the great stuff it can do with its own unmatched cloud intelligence - Now on Tap, for example. Losing that intelligence is what Google's afraid of. Apple is happiest talking about the new platforms and technologies that it wants developers to use - Apple Pay, iBeacons, Extensions or App Search. And losing that developer adoption is what Apple's afraid of.