I think it's because things like Google Maps and Google Search are absolutely dominant in their industry and they try to use default Android apps (forced on man

I think it's because things like Google Maps and Google Search are absolutely dominant in their industry and they try to use default Android apps (forced on manufacturers via the Play Store contract) to try to break into additional industries (like Google+, Photos, etc). The idea being that forcing these additional apps, just to get Play Store is anti-competitive. I'm not sure I'd agree, but there's an argument to be had at least. It's possible Apple could be too, but they've not used this to try to break into as many industries as Google has AFAIK.