Outside of that very narrow context, they may kindly deal with my communications being secured by default, because if there is a path they can use to decrypt my data, the criminals can also find, exploit, and use that same path. Rather easily, as it turns out. (See: various data breaches, password leaks, company after company getting caught with unsecured S3 buckets containing encryption keys, etc etc.) It's not the law I'm hiding from, but those individuals who would steal every one of my digital assets given the opportunity.
In the specific context of Android, the thing I'm trying to dodge isn't even legal snooping or criminal activity, but specifically marketing. Google is terribly interested in my browsing habits, and so having my smartphone not run their services at all is an excellent way to reduce that flow of information from my device to a third party that I don't particularly trust.
Modern surveillance states operate on the premise that every individual, out of billions worldwide, could become a potential threat. To manage this, governments have developed and deployed mass surveillance technologies that far exceed the scope of traditional law enforcement. This environment results in routine circumvention—both legal and extra-legal—of civil liberties and privacy protections, such as the 4th amendment, in the name of national security.
We saw this play out dramatically with the Snowden revelations, which exposed systemic, warrantless collection of communications by agencies such as the NSA. Surveillance is not conducted only for clear national emergencies. It is often routine, preemptive, and opportunistic—and the scale is massive, not targeted only at 'bad actors'.
This reality creates a profound power imbalance. Those who control surveillance infrastructure possess the ability—and in some cases, the legal clearance—to act against individuals or groups for reasons ranging from strategic interests to petty personal motives. There have been numerous documented cases of abuse of surveillance powers by insiders seeking to settle personal scores and, internationally, governments using this capability to quash dissent (for example, China’s censorship and criminalization of government criticism)
Once the technology and precedent for ubiquitous surveillance are in place, the distinction between legitimate and illegitimate use blurs dangerously. The potential for abuse is inherent, especially when oversight is weak or accountability is lacking, which is everywhere.
While companies like Google pose significant privacy concerns and “opting out” of their ecosystems is prudent for reducing commercial data exploitation, the larger threat comes from the normalization of universal, warrantless surveillance by state actors.
Because these states are so extractive of their populace and engage in so much evil that any given person constitutes a potential threat. They're worried that anyone could just wake up one day and decide to be the next uncle Ted or whatever.