Here's a paper describing the privacy invasive and potentially harmful properties of pre-installed apps [1]. I specifically saved this paper in my files so I can have a comprehensive answer when people ask me why I go through the trouble of rooting my devices.
P.S. People who know more than me are saying that the baseband processor can be restricted with hardware practices such as IOMMU [2]. I don't really know how effective that can be.
[1]: https://haystack.mobi/papers/preinstalledAndroidSW_preprint....
The baseband processor isn't running Siri or Google Voice on my phone. Yes, if the state has a back door into the baseband processor there's not much I can do about it, but that's not the threat model that I'm avoiding by not using devices like the Echo or Google Home.
100% this. IF a state intelligence agency is after my data they'll get it somehow (most likely just by asking). My concern is the rampant dragnet aggregation of personal data that I didn't expressly provide them by companies like Google and Facebook. I mean, Google having access to your emails that you store in Gmail? Kind of understandable. Google buying MasterCard transaction records to cross-reference against your web browsing data as tracked by any site using Google Analytics? No.