Strictly speaking, you got me there! Much like narcotic preparations, toxic cosmetics have been known throughout history - so both cases do boil down to the same dynamic after all. (Though there are interesting divergences e.g. in the gendered targeting of the products in question, or their application for altering the state of the self, vs. the perceptions of others, and so on. FWIW I consider both to be harmful and habit-forming; but a habit is a form of personality alteration that must be fairly reckoned with.)

My point is that fighting to get one's unhealthy "toys" back doesn't require any more maturity, self-reflection, or responsible decision-making, than that of a literal toddler. But neither does embodying a "rational economic agent", the very thing notionally expected of well-adjusted adults! This is a compound effect, eventually resulting in the present grossly miscalibrated governance model, where homegrown "growth hackers" run circles around the legislators.

Generously, "think of the children" can be seen as an escape hatch: reverting to some sort of universally shared value to prompt people to reflect on their present choices. Not very effectively, though: "Well I'm building a better future for my children, by selling all of this poison here to your children, what?" And, like one of the parent posters said, consumers don't just stop needing protection once they reach the age of majority. Clearly, we need better consumers.