With regard to your last paragraph: that would probably be an excellent application of Ben Thompson's aggregation theory. It would increase Apple and Google's moat by making them the hardware gatekeeper for all mobile app analytics. And battery life is also a strong cover for the business reasons for doing it.

But the public claim, "it saves battery life!" would not make it defensible for most analytics companies, in my opinion. That would mean Google and Apple get duplicated access to just about all mobile analytics data in the world overnight. They already get vast data from the mobile phones through telemetry and their own apps; I think the largest third party analytics providers would revolt. They would all be at the mercy of Apple and Google's benevolence, which is basically backing their business into a corner. You don't want to be reliant on the whims of a giant tech company.

There are probably also some (maybe weak) anti-trust arguments against it, because all analytics other than e.g. Google Analytics become literal second class citizens on the phone. That would basically be telling app developers they're not allowed to send requests to specific hosts within their apps, only Apple and Google can do that (on their respective phones).

So I don't know if this is a missed opportunity, so much as Apple and Google realizing it would burn their walled gardens to the ground.