As example, the old weather widget from Google's "News & Weather" was replaced by Google Now. That provided a similar experience for some time but then stopped working with another update that required search history to be enabled and/or some other setting in privacy control.
Also the launcher integrated Google with a system update(Moto G line of phones). I have since replaced launcher, browser, search app (all with open source replacements), weather app (with a paid service). Convenience has suffered...
At that point I turned it on but deleted* the search history each day, until such point as they changed the delete controls to be more of a nuisance.
I now use DuckDuckGo and an iPhone instead.
* Or so their site claims.
Your location history tracking is paused..
It can probably save them from a legal mess if they 'resume' it in future updates.
The more specific work I need to go through to set up my privacy, the less inclined I am to do it. If I didn't think I was able to be manipulated psychologically in this way, well, I wouldn't worry about advertising at all! If I were to ever do something politically dissident/personally embarrassing on the internet (not that I ever have of course) I'd go to the trouble of ensuring encryption and being hard to track, but I think it's important that I'm able to say to Google "Hey, I'm cool with you telling me when I should check off work to hit the bar, but it's super weird that you know what I should get my Mom for Mother's Day."
Of course, the simplest way of making a system that's both fine-grained and intuitive might involve... more AI, so I'm not sure how to crack that issue.
This is by design, so that the majority of users are confused and leave the defaults as is, enabling Google to do whatever they like.