The private sector ? Act with fairness ? Have you heard of Facebook ?
If the private sector was intent on acting with fairness we wouldn't need GDPR.
As far as companies are concerned, if it isn't explicitely against the law, it's fair game to try whether it's moral or not. And that is not something that is exclusively reserved to US companies either.
The self-regulating market is a pipe dream served by selfish people intent on preserving their situation - the rest can be damned.
So regulate. Make laws and enforce them. That is the only thing that will protect the people and keep things fair.