Too many companies offer a defense for behavior we find distasteful of, "It isn't illegal," as if the law draws the complete contours of ethical behavior. Generally, we look to laws to dictate punishment for violations of ethics. Of course the law also forbids things we find ethical, but that is another issue.
So no, it won't make social media less addictive, but perhaps it is time we started to formally define what behaviors we consider ethical for these types of interactions between businesses and consumers. With it defined perhaps respectable companies will start to act in the manner we grow to expect.
Those a-holes end up knowing more about your kid than you. And if you try to "fight" them by blocking their access to your kid, they got so many kids hooked up already that the exposure to garbage is unavoidable by some kid whose parents lost the fight or didn't bother to begin with.
A law will protect your kid from gambling in games with "chest full of surprises", and so on.
Of course they can. I won't buy my kids a Javelin from Raytheon, nor a smartphone with Facebook on. With or without laws stopping me.