That’s how it’s often being done. They are doing this in order to prevent government censorship. Same with the equivalent USK (for games) and FSK (for movies) in Germany (which are now powerful enough that it can’t be overruled by the government BPjM anymore, which could previously ban games and other media even if certified by independent rating agencies), MPAA for movies in America (and previously the Hays Code), etc. It’s different in countries like Australia, where the government can directly rate media and thus exert much more influence on it.