I fully understand your argument. It’s the same argument I originally replied to at the top of this discussion. I simply shared my opinion about my conscious choice to stay within the walled garden.

As for your argument, we solve the "government regulation leading to Facebook sucking up your data" problem (if we hypothesize about a future where the user's right to control is enforced through law) with more government regulation (good privacy laws and strict enforcement), not by relying on another private company whose's objectives may change at any time.

Why did it not happen so far?

At least in the US, because of lobbying and potential constitutional issues (Privacy laws that exist in Europe may collide negatively with the First Amendment if passed in America)