Google changed it to be opt-in because they were getting sued left and right and investigated heavily for doing it by default. This wasn't a voluntary choice, G

Google changed it to be opt-in because they were getting sued left and right and investigated heavily for doing it by default. This wasn't a voluntary choice, Google only makes ethical decisions when forced to by an outside party and this was no different. During some of those investigations, it was revealed that even Google engineers found the way Google handled these controls (like the separate Web and App Activity switch) very confusing, leaving ordinary users no hope of understanding it. Finally, Google uses a bit of a carrot and stick method to push people to enable it. Rewards reminds you constantly you're eligible for more surveys/money with location history on, and you can't even have Google Maps default a "home" location locally, without pervasive location tracking being enabled that informs the company where you're at every five minutes. Which is to say, the controls are confusing, the defaults only changed because Google was under investigation, and they make the experience especially on Android if you have it off intentionally terrible.