The Constitution says there will be no code in films as there used to be in the 30s and 40s. It was imposed then because the films were against the accepted moral beliefs of our citizens..
We are now constitutionally free to view pornography in a movie theater....Freedom of speech and dissent has been broadly expanded...Guess which movies make the the most money in America..not R rated or X rated ones..We still have more people wanting to see less porn and glorification of filth.
Those movies make less money because they're age-restricted, thankfully. Not necessarily because less people want to see them.