On his way to get milk, if your son stops along his way, a movie theater won't let him in to see an NC-17 rated film, and they won't let him see an R-rated film

On his way to get milk, if your son stops along his way, a movie theater won't let him in to see an NC-17 rated film, and they won't let him see an R-rated film alone without your consent. A video game retailer won't sell him an AO-rated game, nor will they sell him an M-rated game without your consent. Online game marketplaces have parental controls and gates which rival those used to block streaming of R+ rated commercial films. Why should the law have to double enforce this already deemed successful institutionalized self-policing?