Having ratings applied by a secret cadre hasn't made them all that meaningful either. "Rated PG due to scenes of minor peril." What the fuck does that mean? Is that really useful for information for deciding if you should watch "Ice Age" with your 6 year old? Is the mild peril in "Ice Age" slightly less mild or more perilous than the G-rated "The Lion King"?
PS: I can remember (barely) when movies didn't have ratings. Shocking, right? Oh, and when ratings were new, people understood they were guidelines that had little real meaning. My father took me to see at least one R rated film before I was 10, the only lasting impact of which was an appreciation for the films of Alfred Hitchcock.
I have the impression that most of the time when people say they want to protect children from being exposed to something, what they really want is to protect themselves from having to answer questions that make them uncomfortable.