Sort of by choice. Often, the municipality won't let you build a movie theater unless you pinky-promise to abide by the rating system.
replyThey rarely enforce it, but if it gets out of hand, the city will start getting on your case about it.
Welcome to the world where many countries aren’t the US
replyThe OP is about legislation and companies in the US
replyAnd parent is from the EU and talks about age control in general.
replyDoes the US have a zero-knowledge proof system that is mentioned in the discussion?